I run a Win 7 Ultimate 64 bit VM on my Macbook Pro Retina (2012). It worked quite well, though there has always been some abnormal behaviour in Coherent mode. However, since I upgraded to Mac OSX Mavericks, the VM crashes (it actually just disappears out of memory without trace) after no more then 30 seconds or after not more than 10 mouse clicks. Doesn't matter what I do, starting an application, moving a window, clicking a button, suddenly the VM is just gone. What I noticed is that when I try to restart the VM it looks like it tries to wake up from hibernation or sleep mode. It is not do normal booting. I need to go in the Parallels menu and shutdown (stop) the VM before restarting it. This is curious as I definitely do not send it to sleep! Parallels does of cause detect the crash and send a report. Next time it happens I will copy the report ID and post it here.