I am running Mac OS X 10.5.2 and Fusion 1.1.2 and experienced the same problem. Turned out to be the Last.fm-client, just as in benpoole's case. When the client was shutdown the input from the keyboard worked again in vmware.

These applications works fine together mostly, as long I don't change any preferences in the last.fm client.. But I will inform last.fm about this issue and hopefully this will be solved in their client in a future release.. Thanks for the tips!