You're experiencing errors from your video card driver.
You can try updating the driver from the GPU maker's website, or you can disable OpenGL in Photoshop.
CS6 had nothing to do with it -- CS6 and CS5 don't interfere with one another.
Have seen this exact problem on the forum about 3-4? days ago. Can't remember the solution but had to do with driver. Here is explaination of what you are seeing.
The GPU Sniffer
To help guard against Photoshop crashes related to bad GPU hardware or drivers, Photoshop employs a small program called the GPU Sniffer. Every time Photoshop is launched, Photoshop launches the sniffer. The sniffer runs rudimentary tests of the GPU and reports the results to Photoshop. If the sniffer crashes or reports a failure status to Photoshop, Photoshop will not use the GPU. The Use Graphics Hardware checkbox in the Performance panel of the Preferences will be unchecked and disabled.
The first time the sniffer fails, Photoshop will display a dialog indicating that it has detected a problem with the GPU. On subsequent launches the dialog will not appear unless the Photoshop preferences are reset.
If the user corrects the problem, either by replacing the video card or by updating the driver, then the sniffer will pass on the next launch and the Use Graphics Hardware checkbox will be enabled and returned to its previous state (enabled or disabled).
Thanks so far.
Odd thing is that Ps CS5 32bit works perfectly fine...same workspace, dual monitors, openGL running OK everytime I open normally (no need for reset prefs), but 64 bit is wonky as described above.
There are seperate drivers for 32 bit and 64 bit, and apparently the bug in your drivers is 64 bit only.