I had a problem with VMware Workstation 7.0.1 this weekend. It is a known problem which causes the vmdk to corrupt. This has happened to me a couple times before, but in those cases I just reverted to a snapshot to fix it. This time it was too much work, so I did some research.
Turns out this has been fixed in 7.1.1 build-282343 and fusion 3.1.1 Everyone who is using Workstation 7 or Fusion 3, you should install the latest copy to avoid this issue. In case you have the problem, the fix can be found at: [more]http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1023856