I have a mid-2011 27" iMac i5 base model. On several occassions, when I select "Shut Down" from the apple menu, I get a re-start instead of a shutdown. Before you say I'm likely selecting the wrong item on the menu, I have done some testing where I'm 100-percent positive that I'm selecting the right thing, but it doesn't just shut down, it re-starts. This doesn't happen all the time, but enough to be annoying. There are times when I want to shut down, so I can re-boot in Win 7 under Bootcamp, but I have to shut down a second time after the iMac re-starts instead of shutting down. Has anyone else experienced this problem?