[CentOS] mouse "stuck"

Sommetimes, for no apparent reason, my mouse cursor will become
four arrows and suddenly I cannot do anything with my desktop.
I can move the cursor and that is it.
Clicking has no effect.
cnrtl-alt-F6 gave me another virtual console from which I could post this.
Other rebooting, how do I fix this?
I'm running xfce on 6.2.


-- 
Michael   hennebry at web.cs.ndsu.NoDak.edu
"On Monday, I'm gonna have to tell my kindergarten class,
whom I teach not to run with scissors,
that my fiance ran me through with a broadsword."  --  Lily