Windows Server 2008 R2 guest might not be officially supported yet by VMWare. If that's the case, hope this post could help them improve the support.
I've tried WS2008 R2 Standard (64bits) in VMWare Server 2.0.1 and Workstation 6.5.3
From time to time, my WS2008 would freeze indefinitely. It's not even possible to shut it down. The only way is to suspend it and if a snap-shot exists, go back to previous snap-shot and hope it won't freeze again.
I have no evidence what really caused this, but I have a little idea. It's VMWare Tools.
I noticed the following error event about "side by side":
Activation context generation failed for "C:\Program Files\VMware\VMware Tools\VMControlPanel.cpl". Dependent Assembly Microsoft.VC80.MFC,processorArchitecture="amd64",publicKeyToken="1fc8b3b9a1e18e3b",type="win32",version="8.0.50608.0" could not be found. Please use sxstrace.exe for detailed diagnosis.
When such error happens, WS2008 would freeze sooner or later.
NB: WS2008 freezes more on VMWare Server than on Workstation.