Everyone:

I asked this before under a different heading, and no one answered.

I get a large volume of e-mail, and very often I interact with a site 
that brings up a lot of message boxes, "suggestion boxes" (for 
auto-filling from a few keystroke clues), and bringing up apps after 
they were minimized to the system tray or the task bar. Now why is it 
that, after maybe two hours of operation, those popups come up and are 
totally black? The only way to solve the problem, that I have found, is 
to shut down. And even then, I can't even see what I'm doing, but have 
to guess where the icons are for executing a controlled shutdown. (I can 
always bring up a command-line login screen, log in as root, and then 
shut down. But that doesn't seem to solve the problem for the next session.)

And when I log back on, everything's fine--until it starts happening 
again, after several more window draws.

What could be causing this? Where do I even look for error logs and the 
like?

I never had this problem in any other version of Fedora. I'm having it 
now, and it's driving me nuts.

For the record, I used the "upgrading from F17 to F18 using yum" method. 
I even used the elaborate script that walks you through rpmnew and 
rpmsave reconciliation. And I've kept up with every system update since 
then. Actually, the problem began about three kernel updates back.

Temlakos