Try this - go to control panel, open up "Internet Properties" and then the "Programs" tab.
Click the "Reset Web Settings" button, and check the option: "Internet Explorer should check to see if it is the default browser".
While you're in there, it's probably a wise idea to check your "Add-Ins", Security levels, etc. Take a look at the "Advanced" settings as well.
If all that don't do it for you, get a reliable anti-virus / anti-spyware program, install and run 'cause your browser's probably been hijacked by some form of "MALWARE"
(fyi: AOL is now giving away free versions of McAffee's security suite to anyone and everyone...if u do this, here's a useful hint: AOL's only requirement is that you create a "Screen Name" (and subsequent email account) with them. If you already have one, you can use it. The "Screen Name" / email service is free, and you don't ever have to use it, except for obtaining this program / service. After you successfully create your "Screen Name" you will be at a link to start downloading "McAffee's ....", which won't ever start to download...seems like I went round and round with this , restarting the process over a few times without any luck UNTIL: I BROWSED TO aol.com AND SIGNED IN WITH MY NEW "SCREEN NAME". Then, it all worked (and remains working).
Hopefully, they've done something about this by now, because when I did it, that step didn't exist, and there was nothing even suggesting it: - I was transferred to a page with a button / (link) and some lame error message about not being able to process - try back later, yada, yada, yada....
Good Luck !!!