First, go to tools/Internet options/general tab.
Click on delete browsing history and delete history, cookies and temp files.
Check if you have still problems.
If yes, close IE, click on Start/programs/accessories/system tools and open IE7 without addons from there.
If IE7 works fine, then the fault comes from an addon and you have to find which one is causing the problem.
Then if the problem still occurs, logon on a different account and check.
If no results, then reset IE (you will loose your passwords, config, etc..)
Tools/Internet options/advanced tab/reset.
Hope it helps.