Currently Being ModeratedAug 8, 2012 5:41 PM (in response to Jerry Jewler)
I would run the Apple hardware test to see if it picks up any hardware issues with the video circuit. You'll need the original OS X disks that came with your system to run it.
Currently Being ModeratedAug 8, 2012 7:11 PM (in response to Jerry Jewler)
I agree with BGreg. Run the hardware test that came on the discs that shipped with your iMac.
In addition to running the video tests, also run the RAM memory tests.
It's possible that over the years the RAM modules have moved in their slots slightly with heating/cooling/expansion/contraction, etc. If they have, this is a possible symptom. I would open the RAM access panel on the iMac (Turn It Off And Unplug It First ) and reseat the module(s). It's easy and painless and what have you got to lose?
But I think the direction BGreg is headed is likely... that you may be looking at a graphics card failure.
Good luck. Let us know what you discover.
Currently Being ModeratedDec 30, 2012 2:28 PM (in response to D.I. Johnson)
Mine too. Just started. It is most annoying. It is not so much a wiggle as the entire screen shifts left or right and locks the mouse. I should say locks the mouse buttons (they do nothing), the mouse still moves. It started with the Mt Lion upgrade I think.
Currently Being ModeratedDec 30, 2012 2:32 PM (in response to Claudius2k)
I think I found it. If you go to system preferences / mouse preferences and turn of the check mark for "Swipe Between Full-Screen Apps" I think that will solve your problem.