Taken from the solution over at Lockergnome: 2007 Spell Check Not working

> 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.

This worked for me and got my English U.K. default spelling working again immediately :-)