Here are a few things you can try if you haven't already.
Go to Control Panel/Add/Remove programs
Find IE in the list and click "Change/Remove"
Choose "Repair" from the dialog and run through the process
Note that "sometimes" IE doesn't appear in the Add/Remove Panel.
Go to http://www.microsoft.com/windows/ie/...s/default.mspx
and download/install IE over itself and see if that sorts it out.
Or if you are due to upgrade - use the Windows Update link to upgrade to the latest version.
Take this as a sign that it's time to try/use a "better" browser.
Go to http://www.mozilla.org/
and download/install either Firefox 0.9.1 or Mozilla 1.7 and use one or the other.
I don't think, in the long run you will be disappointed with either.
Built in popup blocker
many more nice features
Sorry I can't be any more help than that -IE is a quirky bugger sometimes.