Mac Pro (mid 2010) grinds to a halt when display is rotated to portrait I have a Mac Pro Mid 2010 with two ATI Radion 5770's driving 6 Dell U2412M's. Problem is, when even just one of these displays is rotated to portrait, the entire system grinds to a halt. CPU usage spikes to about 85%, I have 12gb of RAM installed and when this happens, about 512mb is free. And graphics performance is all but completely dead. At first I thought this may be because I am driving six monitors at once. But this is illogical be cause for one, it only just started occurring since I upgraded to 10.8(which as a power user, I absolutely hate). And two because this also happens with just one monitor hooked up. Any ideas?
This is the sort of thing a well documented bug would let an engineer fix the code to avoid crippling a powerful Mac with a video change.


https://developer.apple.com/bugreporter/
Once you have the machine blocked, type sudo sysdiagnose in terminal and send that output in with the bug report as an attachment.
Usually, you never hear back, but sometimes you'll get an email requesting more details to help engineering isolate the behavior you are seeing.