[CentOS] keyboard problem

OK, I know what I'm doing is "officially unsupported", but perhaps someone 
has some suggestions...

I have a CentOS 5.6 system running as a virtual machine using VMware 
player.  I cloned the system, booted the clone to make sure everything 
worked after cloning, it did.  I then booted off a CentOS 6 ISO and did an 
upgrade (I know, unsupported!).  I've got the system to the point where 
everything works except the keyboard.

If I boot to a command line, it works, as soon as X gets involved, there 
is no response at all from the keyboard.  The on-screen keyboard does 
work.  The physical keyboard works in the host OS and all of the other 
guest OSes on the machine.  It works in the original CentOS 5.6 VM.  

I'm at a loss and would love some advice on where to look next.

Thanks!
Bruce