First thing to try is to Reset Defaults for IE
1. Close any Internet Explorer or Windows Explorer windows that are currently open.
2. Open Internet Explorer by clicking the Start button Picture of the Start button, and then clicking Internet Explorer.
3. Click the Tools button, and then click Internet Options.
4. Click the Advanced tab, and then click Reset.
5. Select the Delete personal settings check box if you would like to remove browsing history, search providers, Accelerators, home pages, and InPrivate Filtering data.
6. In the Reset Internet Explorer Settings dialog box, click Reset.
7. When Internet Explorer finishes applying default settings, click Close, and then click OK.
8. Close Internet Explorer.
Your changes will take effect the next time you open Internet Explorer.
That should do it
Assuming you are using XP or Vista
If that does not work out, I would try to uninstall IE8 from add/remove programs (will bring back to previous version)
Now at this point, try to see if it will work with previous version
If everything is working all right, reinstall IE8
If not, will go from there