[CentOS] Centos 5 File Server X-Windows problem

I have a file server that runs a virtual machine that suddenly blanked 
its display.  I can switch to <ctrl><alt><f1>, but switching back to 
<ctrl><alt><f7> just gives me a blank screen (no cursor).  There are no 
entries in /var/log/messages or in /var/log/Xorg.0.log that might 
explain what happened.  I was running IceWM, but I can't find any logs 
for it at all.  ~/.xsession-errors shows nothing useful, either.  ( And 
was last updated 10 days ago. )

Anyone have an idea what happened?  ( Or how to figure out what happened? )