Screen Image Breaks Up When Outlook Express Checks Mail

[JaeBon]

This is a strange question, but I am really puzzled. I have Windows XP and Outlook Express 6. Recently when Outlook Express checks email, my screen image goes completely blank, to the background color; if I roll the mouse over the screen, parts of the image become visible. This happens even if Outlook Express is minimized--whatever image is on the screen dissolves like this. I have McAfee VirusScan protection, Sygate Personal Firewall, and I run Ad-Aware and SpyBot frequently. Any ideas? Thanks for taking time to read my message.