Microsoft offers a free technical advice line devoted to explorer 8 problems, fortunately they managed to cure the problem for me, apparently the fault was in the download.
I also had the same problem some time ago. I just can't live without my IE add-ons. I'm using:
LeechVideo
– cool IE addon that lets you download favorite videos from popular
video sharing websites ( i.e. Youtube, Google Video, etc.)
Billeo - Password Management, Shopping, & Bill Pay Toolbar for Windows. It features an encrypted Password Manager, eWallet with
1-click Form Fill, and the ability to Save and Search online receipts
and web pages.
Inline Search
– integrates an in-page search feature to Internet Explorer.