Ok, so I was right about the Combo updater - wouldn't install on my system.
So I tried all your other suggestions (well, except for installing Yosemite) and no go, although I'm not sure that resetting my file and folder permissions worked properly (I waited 15 mins and still didn't get the 'reset' button back again, so I just continued on with the rest of the steps).
Here is my Etrecheck results:
EtreCheck version: 2.1.8 (121)
Report generated 23 March 2015 9:59:21 pm AEST
Download EtreCheck from http://etresoft.com/etrecheck
Click the [Click for support] links for help with non-Apple products.
Click the [Click for details] links for more information about that line.
Hardware Information: ℹ️
iMac (21.5-inch, Mid 2010) (Technical Specifications)
iMac - model: iMac11,2
1 3.06 GHz Intel Core i3 CPU: 2-core
12 GB RAM Upgradeable
BANK 0/DIMM0
2 GB DDR3 1333 MHz ok
BANK 1/DIMM0
4 GB DDR3 1333 MHz ok
BANK 0/DIMM1
4 GB DDR3 1333 MHz ok
BANK 1/DIMM1
2 GB DDR3 1333 MHz ok
Bluetooth: Old - Handoff/Airdrop2 not supported
Wireless: en1: 802.11 a/b/g/n
Video Information: ℹ️
ATI Radeon HD 4670 - VRAM: 256 MB
iMac 1920 x 1080
System Software: ℹ️
OS X 10.9.5 (13F1066) - Time since boot: 0:12:30
Disk Information: ℹ️
ST3500418AS disk0 : (500.11 GB)
EFI (disk0s1) <not mounted> : 210 MB
Macintosh HD (disk0s2) / : 499.25 GB (190.97 GB free)
Recovery HD (disk0s3) <not mounted> [Recovery]: 650 MB
OPTIARC DVD RW AD-5680H
USB Information: ℹ️
ASMedia AS2105 1 TB
EFI (disk2s1) <not mounted> : 210 MB
Digital Media (disk2s2) /Volumes/Digital Media : 999.86 GB (274.31 GB free)
Samsung M3 Portable Samsung M3 Portable 2 TB
EFI (disk1s1) <not mounted> : 210 MB
iMac 2TB TM Backup (disk1s2) /Volumes/iMac 2TB TM Backup : 2.00 TB (753.92 GB free)
Apple Inc. BRCM2046 Hub
Apple Inc. Bluetooth USB Host Controller
Apple Internal Memory Card Reader
INNO TECH USB to Serial
Apple Inc. Built-in iSight
Apple Computer, Inc. IR Receiver
Gatekeeper: ℹ️
Anywhere
Kernel Extensions: ℹ️
/Library/Application Support/VirtualBox
[loaded] org.virtualbox.kext.VBoxDrv (4.3.20) [Click for support]
[loaded] org.virtualbox.kext.VBoxNetAdp (4.3.20) [Click for support]
[loaded] org.virtualbox.kext.VBoxNetFlt (4.3.20) [Click for support]
[loaded] org.virtualbox.kext.VBoxUSB (4.3.20) [Click for support]
/Library/Extensions
[loaded] com.usboverdrive.driver.hid (3.1 - SDK 10.8) [Click for support]
/Library/Extensions/USBOverdrive.kext/Contents/PlugIns
[loaded] com.usboverdrive.driver.bt (3.1 - SDK 10.8) [Click for support]
[not loaded] com.usboverdrive.driver.hid.safe (3.1) [Click for support]
/System/Library/Extensions
[not loaded] com.Belcarra.iokit.USBLAN_netpart (3.1.1 - SDK 10.6) [Click for support]
[not loaded] com.Belcarra.iokit.USBLAN_usbpart (3.1.1 - SDK 10.6) [Click for support]
[not loaded] com.RemoteControl.USBLAN.usbpart (3.1.1 - SDK 10.7) [Click for support]
[loaded] com.orderedbytes.driver.ControllerMateFamily (4.6.0 - SDK 10.6) [Click for support]
[loaded] com.squirrels.airparrot.framebuffer (3 - SDK 10.7) [Click for support]
[loaded] com.squirrels.driver.AirParrotSpeakers (1.7 - SDK 10.7) [Click for support]
[loaded] com.techsmith.TACC (1.0.2 - SDK 10.8) [Click for support]
[not loaded] com.ups.driver.UPSVendor (1.0.0d1) [Click for support]
/System/Library/Extensions/2.2.0/Belcarra.USBLAN_netpart.kext/Contents/Plug-Ins
[not loaded] com.belcarra.iokit.netpart.panther (1.6.3) [Click for support]
/System/Library/Extensions/2.2.0/Belcarra.USBLAN_usbpart.kext/Contents/Plug-Ins
[not loaded] com.belcarra.iokit.usbpart.panther (1.6.3) [Click for support]
/System/Library/Extensions/2.2.0/RemoteControl.USBLAN_usbpart.kext/Contents/Plu g-Ins
[not loaded] com.RemoteControl.USBLAN.panther (1.6.2) [Click for support]
/System/Library/Extensions/ControllerMate.kext/Contents/PlugIns
[loaded] com.orderedbytes.driver.CMUSBDevices (4.6.0 - SDK 10.6) [Click for support]
[not loaded] com.orderedbytes.driver.CMUSBKeyboard (4.6.0 - SDK 10.6) [Click for support]
[not loaded] com.orderedbytes.driver.CMUSBPointer (4.6.0 - SDK 10.6) [Click for support]
Launch Agents: ℹ️
[not loaded] com.adobe.AAM.Updater-1.0.plist [Click for support]
[loaded] com.adobe.CS5ServiceManager.plist [Click for support]
[running] com.orderedbytes.ControllerMateHelper.plist [Click for support]
[running] com.parallels.mobile.prl_deskctl_agent.launchagent.plist [Click for support]
[not loaded] com.teamviewer.teamviewer.plist [Click for support]
[not loaded] com.teamviewer.teamviewer_desktop.plist [Click for support]
Launch Daemons: ℹ️
[loaded] com.adobe.fpsaud.plist [Click for support]
[not loaded] com.adobe.SwitchBoard.plist [Click for support]
[loaded] com.microsoft.office.licensing.helper.plist [Click for support]
[running] com.netputing.handyPrintSystemDaemon.plist [Click for support]
[loaded] com.oracle.java.JavaUpdateHelper.plist [Click for support]
[running] com.parallels.mobile.dispatcher.launchdaemon.plist [Click for support]
[loaded] com.parallels.mobile.kextloader.launchdaemon.plist [Click for support]
[loaded] com.quark.quarkupdate.plist [Click for support]
[loaded] com.teamviewer.Helper.plist [Click for support]
[not loaded] com.teamviewer.teamviewer_service.plist [Click for support]
[not loaded] org.virtualbox.startup.plist [Click for support]
User Launch Agents: ℹ️
[failed] com.acronis.monitor.plist [Click for support]
[loaded] com.adobe.AAM.Updater-1.0.plist [Click for support]
[loaded] com.adobe.ARM.[...].plist [Click for support]
[loaded] com.google.keystone.agent.plist [Click for support]
[running] com.parallels.mobile.startgui.launchagent.plist [Click for support]
[not loaded] org.virtualbox.vboxwebsrv.plist [Click for support]
User Login Items: ℹ️
iTunesHelper Application (/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)
Dropbox Application (/Applications/Dropbox.app)
DVDAuthorizeHelper Application (/Users/[redacted]/Library/Application Support/Helper/DVDAuthorizeHelper.app)
Wondershare Helper Compact Application (/Users/[redacted]/Library/Application Support/Helper/Wondershare Helper Compact.app)
USBOverdriveHelper Application (/Library/PreferencePanes/USB Overdrive.prefPane/Contents/Resources/USBOverdriveHelper.app)
Internet Plug-ins: ℹ️
JavaAppletPlugin: Version: 14.9.0 - SDK 10.7 Check version
FlashPlayer-10.6: Version: 17.0.0.134 - SDK 10.6 [Click for support]
QuickTime Plugin: Version: 7.7.3
Flash Player: Version: 17.0.0.134 - SDK 10.6 [Click for support]
AdobePDFViewer: Version: 9.5.5 [Click for support]
Default Browser: Version: 537 - SDK 10.9
SharePointBrowserPlugin: Version: 14.4.8 - SDK 10.6 [Click for support]
Silverlight: Version: 5.1.30514.0 - SDK 10.6 [Click for support]
iPhotoPhotocast: Version: 7.0 - SDK 10.8
User internet Plug-ins: ℹ️
Google Earth Web Plug-in: Version: 7.1 [Click for support]
Safari Extensions: ℹ️
1Password
Open in Internet Explorer
Video Converter
3rd Party Preference Panes: ℹ️
Flash Player [Click for support]
Quark Update Preferences [Click for support]
USB Overdrive [Click for support]
Time Machine: ℹ️
Skip System Files: NO
Mobile backups: OFF
Auto backup: YES
Volumes being backed up:
Macintosh HD: Disk size: 499.25 GB Disk used: 308.27 GB
Digital Media: Disk size: 999.86 GB Disk used: 725.55 GB
Destinations:
iMac 2TB TM Backup [Local]
Total size: 2.00 TB
Total number of backups: 36
Oldest backup: 2015-03-11 08:48:55 +0000
Last backup: 2015-03-23 10:17:51 +0000
Size of backup disk: Too small
Backup size 2.00 TB < (Disk used 1.03 TB X 3)
Top Processes by CPU: ℹ️
2% WindowServer
1% fontd
1% hidd
0% AppleSpell
0% com.apple.WebKit.Networking
Top Processes by Memory: ℹ️
180 MB com.apple.IconServicesAgent
168 MB Mail
168 MB Safari
129 MB com.apple.WebKit.WebContent
90 MB com.apple.WebKit.Networking
Virtual Memory Information: ℹ️
7.36 GB Free RAM
3.94 GB Active RAM
692 MB Inactive RAM
892 MB Wired RAM
421 MB Page-ins
0 B Page-outs
Diagnostics Information: ℹ️
Mar 23, 2015, 09:47:43 PM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-23-21 4743_[redacted].crash
Mar 23, 2015, 09:47:31 PM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-23-21 4731_[redacted].crash
Mar 23, 2015, 09:46:19 PM Self test - passed
Mar 23, 2015, 08:59:14 PM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-23-20 5914_[redacted].crash
Mar 23, 2015, 06:06:37 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-23-06 0637_[redacted].crash
Mar 23, 2015, 06:06:36 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-23-06 0636_[redacted].crash
Mar 22, 2015, 07:18:59 PM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-19 1859_[redacted].crash
Mar 22, 2015, 07:09:35 PM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-19 0935_[redacted].crash
Mar 22, 2015, 08:32:46 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-08 3246_[redacted].crash
Mar 22, 2015, 08:32:35 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-08 3235_[redacted].crash
Mar 22, 2015, 07:33:06 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-07 3306_[redacted].crash
Mar 22, 2015, 07:33:05 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-07 3305_[redacted].crash
Mar 22, 2015, 07:32:55 AM /Library/Logs/DiagnosticReports/com.netputing.handyPrintProDaemon_2015-03-22-07 3255_[redacted].crash
Anyway, I'm gonna try the whole reset of my files and folders again and leave it a lot longer this time and see what happens.
Joe.
PS. Thanks again for all your help!