Strange Problem: Mac OSX work at VMWare 5 at home but

I found, downloaded and ran a MacOS X VMWare 5 virtual machine disk set at home, and it worked perfectly. But when I bring the same VMWare machine to the office, I got error from VMWare 5 saying that the virtual disk is not vaild. Man, I was really puzzled.

BTW, even though the MacOSX runs fine under VMWare 5, it's just too slow to be really enjoyable. It's fun to see Mac OSX running on a PC, but other than the thrill factor, I don't see any usage for it.