A Microsoft Word 2007 spell check does not work

Here is a solution if you're willing to do a minor edit to the registary:

HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\ProofingTools\1.0\Override\en-US

I had 2 entries (DLL and LEX) pointing to non-existing files. Delete these entries. After this change all Spell Checking worked normal again.