Im surprised if it only happens on ebay, i expect it to be some third party plugin that has caused the problem, as ebay has flash on the front page maybe it macromedia flash plugin - scan you view other pages with flash?
Try going to add/remove programs and then go to Internet Explorer, then choose uninstall, you should have an option to "repair" when you do this - try that and se if it fixes your problem.
Failing all that download firefox, an excellent browser (in my opinion far better than IE and free) or redownload iE and try installing it again.
hope some of that helped
matt