I to am having the same problem. I can be working in my Windows 7 VM for some time but suddenly my entire gnome-shell session will freeze and will not come back to life. In order to resolve I simply do ALT+CTL+PRINT SCREEN+K to restart the session. This is really becoming a pain in the butt and would love some kind of resolution.
If someone finds a resolution please share!!
model name : AMD FX(tm)-8120 Eight-Core Processor
MemTotal: 8139292 kB
DISTRIB_CODENAME=lisa
DISTRIB_DESCRIPTION="Linux Mint 12 Lisa"
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=12
VMware Workstation 8.0.1 build-528992
Linux mint 3.0.0-12-generic #20-Ubuntu SMP Fri Oct 7 14:56:25 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
01:00.0 VGA compatible controller: nVidia Corporation G92 [GeForce 9800 GTX] (rev a2)