FC2, KDE, ATI: can't move/resize windows on one screen in dual head

[James Jones]

My wife's computer has FC2, and she prefers KDE. I have set her up with 
an ATI Radeon 7500 graphics card, and now have it going in dual head mode.

We now find that sometimes, she is unable to move or resize windows on 
one screen. We already know about not being able to move windows from 
one screen to another; that's a shame, but we can live with it. This 
isn't that; windows opened on one screen refuse to move or resize at 
all. Windows opened on the other screen, OTOH, work fine.

If she logs out and logs back on, the problem goes away, at least for a 
while.

What could be causing this?

    James Jones