X starts denying me access

[dmorin at lear.morinfamily.com (Duane Morin)]

I'll be running just fine for hours on my Redhat 9 laptop, opening windows 
at will.  Then all of a sudden I'll try to do something that requires 
a window opening and get 

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
 
Application initialization failed: couldn't connect to display ":0.0"


I've done nothing different, and this error is thrown by the exact same 
shell that 5 minutes ago let me open a window just fine.

What could be going on behind the scenes that's causing this?  I should 
mention that when I say "opening windows at will" I don't mean hundreds, I 
mean a handful - maybe a dozen, tops.  And, right now, there's maybe 5 
open.

Duane