It just happened at a random time, while adjusting the slips. Those squares appeared. The orange you see through it is my background. I moved the window and it disappeared.
At least it didn't crashed this time.
Just thought I would share with you.
Good Luck
Macbook pro mid 2010 with 2.5ghz 330M and 8 Gb of ram on lion 10.7.1 all last update. So it is nvidia not ati.Also I'm editing native Avchd footage from GH2 (unhooked at the time so 24mbps)