Considering the huge user base for Quicktime and the fact that only a few dozen users have posted here, the problems described in these forums do not appear to be confined to users of either Leopard or Tiger, or either PPC or Intel Macs, but relatively speaking they are few and far between. I have had no problems at all after installing QT 7.5.
it is therefore reasonable to assume that something in either your pre-existing setup or your method of installing updates, are the root causes of whatever problems you are having with QT 7.5 particularly with choppy playback. Out of date plug-ins and add-ons could also be playing a part.
A few things to try but in each case first close all applications and repair permissions.
1 Try opening then closing GarageBand, or launching then quitting the "Audio MIDI Setup" application located in Applications/Utilities. Failing that, go back to Audio MIDI Setup, and under the Audio Devices tab, make sure the Audio Output Format is 44100.0 2ch-16bit.
Restart your Mac.
2 Go to the Library on your main hard disk and find the Internet Plug-Ins folder. Try removing the following files:
QuickTime plugin.plugin
Quicktime plugin.webplugin
Restart your Mac.
Re-install the Quicktime 7.5 update
Go to Home/Library/Receipts and delete the file Quicktime 7.5 pkg.
Download from the Download page on the Apple site the correct version of Quicktime 7.5 for your Mac.
Install it and restart your Mac. Repair permissions.
3 If still no luck, it is time to look carefully at your plug-ins and add-ons. The safest way is to download and re-install all of them. The ones you need in order to see and hear virtually everything the web has to offer are:
RealPlayer 11 (which is no longer in beta) for Mac from (you may need a different site for the US):
http://uk.real.com/player/mac/
Flip4Mac WMV Player from
http://www.microsoft.com/windows/windowsmedia/player/wmcomponents.mspx (Windows Media Player for the Mac is no longer supported, even by Microsoft)
Perian from
http://perian.org/
You should read this support page
http://perian.org/#support in case you need to delete older codecs.
Adobe FlashPlayer should first be uninstalled using the appropriate uninstaller available here:
http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_14157&sliceId=2 and then the latest version obtained from here:
http://www.adobe.com/shockwave/download/download.cgi?P1ProdVersion=ShockwaveFlash and installed.
(You can check here:
http://www.adobe.com/products/flash/about/ to see which version you should install for your Mac and OS.)
You should also ensure that you have downloaded and installed all the correct version for your Mac of all recent Security Updates.
(N.B. Security Updates require both a restart and a permission repair.)
In Macintosh HD/Library/Quicktime/ delete any files relating to DivX (Perian already has them). However it should be noted that Perian is not an internet plugin and will not play DivX files imbedded on a website. For that you will need the DivX Player browser plugin available from
http://www.divx.com/divx/mac/
Now go to Safari Preferences/Security, and tick the boxes under Web Content (all 4 of them) to enable Java.
Lastly open Audio Midi Setup (which you will find in the Utilities Folder of your Applications Folder) and click on Audio Devices. Make sure that both Audio Input and Audio Output, under Format, are set to 44100 Hz, and that you have selected 'Built in Audio'.
Important: Now repair permissions and restart.
There is an additional 'fix' you could try if you are having problems with Flash and Quicktime, depending on which type of Mac you have:
On Intel Macs, make sure that you are not running Safari in Rosetta. You can check this, and change it, in the Get Info window.
On PPC Macs, go to the Hard Disk/Library/Internet Plug-Ins folder, and drag the file 'QuickTime Plugin.webplugin' to the desktop. Quit and restart Safari. If things have improved you can trash that file. If they haven't put it back, as the lack of this plug-in can cause QT content in some widgets to cease functioning.
If none of the foregoing worked, then you should consider and archive and install before repeating all of the above.
