2007 Spell Check Not working

Start Regedit and goto the following key:
HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\Proofing
Tools\1.0\Override\en-US

I had 2 entries (DLL and LEX) pointing to non-existing files.

Rename these to oldDLL and oldLEX.

After this change all Spell Checking worked normal again.

Source: http://help.lockergnome.com/office/2007-Spell-Check-working-ftopict928009.html