How many instances of parallels have people managed to get running. On a MacBook Pro with 3 GB of RAM, having a FreeBSD and a Windows XP session brings the machine to a crawl, though I have managed to eek in a third one. On a Mac Pro with 16 GB of RAM and 4 cores I can get 5 going, but when I try to add a 6th, I get very strange failures that are very ungraceful. Sometimes when I boot the sixth up and try an install of an OS, it fails randomly (when I have done the exact same install on VM #4 and it works). Other times it crashes and says report this to parallels. Most often it actually crashes the WindowServer process and causes the entire GUI to lock. What have you experienced when you try to run many instances of Parallels on the same Mac?