What was the last thing you did before the problem first occured.
Are you getting any error messages?
Have you run any ati-virus or spyware scans?
You may want to try repairing OE. See http://www.theeldergeek.com/repair_reinstall_ie_and_oe_6.htm If you attempt a repair you may first want to backup email files.
Outlook Express 6.0 is acting weird. If I minimize it to surf the net, the buttons are bigger when I go back to it. Then, if I minimize it again and come back to it, they are even larger. It does this whether I have it set to large or small icons. The buttons grow so large that only a couple can even be displayed on the page.
I have Windows XP Media Edition, all th latest updates. HP Pavilion a1510n that I bought in Nov.