I think there is a memory leak in parallels desktop 6. When I start using windows 7 x64 on parallels 6 i have 1.5 gb ram free. After 30 minutes it goes down to 900 mbs ram free. I have 4 gb ram total and i have set parallels to use 1 gb for my windows 7. Also I do not have any other applications running in osx.
Having the same issue Running PD6, limited VM to 3gb of use on an 8gb MBP- Once VM boots, my Ram is overwhelmed and everything freezes up. Not running any other applications. Build 6.0.12106