I had a similar problem with an Office 2007 upgrade.
I searched and looked searched to try and determine if it was a local
problem, if I needed additional software, if other users had the same issue
and so on.
Ultimately I tried two things:
1 - I ran Microsoft Office Diagnostics tool (All Programs.. Microsoft
Office.. Microsoft Office Tools) - this reported 1 error and 1 fix but I do
not know what that was - it did not fix my problem.
2 - I renamed the registry entry "HKEY_CURRENT_USER\Software\Microsoft\Shared
Tools\Proofing Tools\1.0" (changed it to "1.0-bad") - this fixed the
problem. The next time I tried Spell Check it worked and added the correct
I hope this helps those in a similar situation.