I have had this issue a number of times and it is getting more than a
bit annoying.

System:  FC5 - have updated everything within the last couple of weeks
with yum.

I am working along ... at some point the system seems to lock up - after
a fashion.  I can still move the mouse and the arrow is moving
around ... the color of the mouse changes indicating I can move it
across windows and that is detected ... but ... I can not select any of
the windows open on the screen.  It is like the mouse button feature is
gone. 

I eventually get annoyed ... reset X via ctl-alt-backspace to kill X,
relog in and then everything is fine.

Thoughts?  Suggestions?  Thanks in advance.

Randy