Thanks for the many good suggestions. Alt-Ctl-Esc and Alt-Ctl-F1 do not 
work once the mouse has frozen. It is probably more like Xorg has 
frozen. The mouse has not been changed and xorg.conf looks to be 
correct. Legacy USB support was not enabled in the bios. It is 
definitely an Xwindows/Xorg problem, because nongraphical system works 
with no problem, even the mouse works if not running Xwindows.

Gary