Black bar appearing over Menubar on Acrobat 8

I recently upgraded to Acrobat 8, which I love by the way. But every so often when using it, my menubar becomes totally blackened out -- not from one edge of the screen to the other, but only over the words... from File to Help. If I mouse over the menubar, it will appear one word at a time (the word I'm currently hovering over) and it will work. Bu then when I take my mouse away, it's all totally black again. If I close Acrobat and then reopen, it goes away. But it eventally comes back. I haven't quite figured out what triggers it.

In the installation I did elect to uninstall Acrobat 7. All updates are installed. I repaired the installation as well and that didn't help.

Any suggestions would be appreciated! Thank you!