Part of Internet Explorer's program has become corrupted. Try resetting Internet Explorer as follows:
Click here:
http://go.microsoft.com/?linkid=9646978
In the File Download dialog box, click Run, and then follow the steps in the wizard.
In the Reset Internet Explorer Settings dialog box, click Reset.
When Internet Explorer finishes applying the default settings, click Close, and then click Close again.
Close and then start Internet Explorer.
Alternatively, why not simply use a decent browser anyway, rather than the totally dire Internet EXplorer? Most of the 'regulars', here in AB's Technology section, wouldn't touch Internet Explorer with a million of the proverbial bargepoles. Firefox is much, much better:
http://www.mozilla.org/en-US/firefox/all/