|It could be caused by malware or possibly a mis-behaving add-on. |
Run any malware scans you fancy - AdAware & SpyBot if you haven't already got a security suite.
If it's still misbehaving then start by uninstalling any toolbars, such as Yahoo, Google etc from Add/remove programs.
If still no good then go to Control Panel, Internet Options, on the 'Advanced' tab click the 'reset' buttons - it restores IE to its original state, without any add-ons.
One of the above should fix it..
"I've always been mad, I know I've been mad, like the most of us..."