What's causing kernel panic on mid 2011 iMac? (a freed zone element has been modified) I've got a mid 2011 iMac that kernel panics roughly after 30 to 45mins of being powered on. Then the panics seem to get worst eg after every restart of the imac.

I've tried x2 different boot drives both using OS X 10.10.5 as the base system, one being a USB drive and other being a thunderbolt drive.

At the moment my theories are it's more of a hardware problem then software, either ram or possible gpu. 

See screenshot of report below:
This turned out to be one piece of bad ram installed in the iMac.