iMac keeps freezing/crashing

Hi,

I would really appreciate some support from anyone,

My iMac has been crashing for sometime now, usually when i'm watching something online or playing a game. At first I thought I needed to upgrade my OS to Yosemite which I did but the issue has not resolved. So I completely wiped my iMac and restored to factory settings. I tried to use it again (just watching a stream clip online) and it completely froze and then restarted itself giving the following report - any insight into my issue would be greatly appreciated - I'm literally on the verge of just getting rid of it!! Thank you.

Anonymous UUID: 2A4A2A93-5C9A-CEC0-4F97-923BBF82F085

Thu May 7 01:40:33 2015

*** Panic Report ***

panic(cpu 1 caller 0xffffff801096cffd): "a freed zone element has been modified in zone kalloc.256: expected 0x3f0011aa45ba360a but found 0, bits changed 0x3f0011aa45ba360a, at offset 248 of 256 in element 0xffffff8022f59100, cookies 0x3f0011aa45ba360a 0x53521f598aa917f"@/SourceCache/xnu/xnu-2782.20.48/osfmk/kern/zalloc.c:496

Backtrace (CPU 1), Frame : Return Address

0xffffff80aa0cbdf0 : 0xffffff801092bda1

0xffffff80aa0cbe70 : 0xffffff801096cffd

0xffffff80aa0cbee0 : 0xffffff801096a132

0xffffff80aa0cbf90 : 0xffffff80109c9eb9

0xffffff80aa0cbfb0 : 0xffffff8010a125b7

BSD process name corresponding to current thread: kernel_task

Mac OS version:

14D136

Kernel version:

Darwin Kernel Version 14.3.0: Mon Mar 23 11:59:05 PDT 2015; root:xnu-2782.20.48~5/RELEASE_X86_64

Kernel UUID: 4B3A11F4-77AA-3D27-A22D-81A1BC5B504D

Kernel slide: 0x0000000010600000

Kernel text base: 0xffffff8010800000

__HIB text base: 0xffffff8010700000

System model name: iMac9,1 (Mac-F2218FC8)

System uptime in nanoseconds: 3659296853754

last loaded kext at 275314137442: com.apple.filesystems.msdosfs 1.10 (addr 0xffffff7f92fa3000, size 69632)

last unloaded kext at 335966961555: com.apple.filesystems.msdosfs 1.10 (addr 0xffffff7f92fa3000, size 61440)

loaded kexts:

com.apple.driver.AudioAUUC 1.70

com.apple.driver.AppleHWSensor 1.9.5d0

com.apple.driver.AGPM 110.19.5

com.apple.filesystems.autofs 3.0

com.apple.iokit.IOBluetoothSerialManager 4.3.4f4

com.apple.driver.AppleOSXWatchdog 1

com.apple.driver.AppleMikeyHIDDriver 124

com.apple.driver.AppleHDA 272.18

com.apple.driver.AppleMikeyDriver 272.18

com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport 4.3.4f4

com.apple.iokit.IOUserEthernet 1.0.1

com.apple.Dont_Steal_Mac_OS_X 7.0.0

com.apple.driver.AppleHWAccess 1

com.apple.driver.AppleHV 1

com.apple.driver.AppleUpstreamUserClient 3.6.1

com.apple.driver.ACPI_SMC_PlatformPlugin 1.0.0

com.apple.driver.AppleLPC 1.7.3

com.apple.driver.AppleIntelSlowAdaptiveClocking 4.0.0

com.apple.driver.AppleBacklight 170.7.4

com.apple.driver.AppleMCCSControl 1.2.11

com.apple.GeForceTesla 10.0.0

com.apple.AppleFSCompression.AppleFSCompressionTypeDataless 1.0.0d1

com.apple.AppleFSCompression.AppleFSCompressionTypeZlib 1.0.0d1

com.apple.BootCache 36

com.apple.driver.AppleIRController 327.5

com.apple.iokit.SCSITaskUserClient 3.7.5

com.apple.driver.XsanFilter 404

com.apple.iokit.IOAHCIBlockStorage 2.7.1

com.apple.driver.AppleUSBHub 705.4.2

com.apple.driver.AirPort.Brcm4331 800.20.24

com.apple.driver.AppleFWOHCI 5.5.2

com.apple.driver.AppleAHCIPort 3.1.2

com.apple.driver.AppleUSBOHCI 656.4.1

com.apple.nvenet 2.0.22

com.apple.driver.AppleUSBEHCI 705.4.14

com.apple.driver.AppleHPET 1.8

com.apple.driver.AppleRTC 2.0

com.apple.driver.AppleACPIButtons 3.1

com.apple.driver.AppleSMBIOS 2.1

com.apple.driver.AppleACPIEC 3.1

com.apple.driver.AppleAPIC 1.7

com.apple.driver.AppleIntelCPUPowerManagementClient 218.0.0

com.apple.nke.applicationfirewall 161

com.apple.security.quarantine 3

com.apple.security.TMSafetyNet 8

com.apple.driver.AppleIntelCPUPowerManagement 218.0.0

com.apple.AppleGraphicsDeviceControl 3.10.22

com.apple.kext.triggers 1.0

com.apple.iokit.IOSerialFamily 11

com.apple.driver.DspFuncLib 272.18

com.apple.kext.OSvKernDSPLib 1.15

com.apple.iokit.IOBluetoothHostControllerUSBTransport 4.3.4f4

com.apple.iokit.IOSurface 97.4

com.apple.iokit.IOBluetoothFamily 4.3.4f4

com.apple.driver.AppleHDAController 272.18

com.apple.iokit.IOHDAFamily 272.18

com.apple.iokit.IOAudioFamily 203.3

com.apple.vecLib.kext 1.2.0

com.apple.driver.IOPlatformPluginLegacy 1.0.0

com.apple.driver.AppleSMBusPCI 1.0.12d1

com.apple.driver.IOPlatformPluginFamily 5.9.1d7

com.apple.iokit.IOSlowAdaptiveClockingFamily 1.0.0

com.apple.iokit.IOFireWireIP 2.2.6

com.apple.driver.AppleBacklightExpert 1.1.0

com.apple.driver.AppleSMC 3.1.9

com.apple.driver.Apple

Model: iMac9,1, BootROM IM91.008D.B08, 2 processors, Intel Core 2 Duo, 3.06 GHz, 4 GB, SMC 1.37f3

Graphics: NVIDIA GeForce GT 130, NVIDIA GeForce GT 130, PCIe, 512 MB

Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334448312D4346382020

Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1067 MHz, 0x80CE, 0x4D34373142353637334448312D4346382020

AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x8E), Broadcom BCM43xx 1.0 (5.106.98.100.24)

Bluetooth: Version 4.3.4f4 15601, 3 services, 27 devices, 1 incoming serial ports

Network Service: Wi-Fi, AirPort, en1

Serial ATA Device: WDC WD1001FALS-40K1B0, 1 TB

Serial ATA Device: OPTIARC DVD RW AD-5670S

USB Device: Built-in iSight

USB Device: My Book 1110

USB Device: Keyboard Hub

USB Device: Apple Optical USB Mouse

USB Device: Apple Keyboard

USB Device: IR Receiver

USB Device: BRCM2046 Hub

USB Device: Bluetooth USB Host Controller

Thunderbolt Bus: