Tools>Options>Spelling>Languages used to have a list of available and installed languages. I noticed recently that the list now has only the four I installed for "English" and none listed as "available". In the Vista forums, Brink had posted a tutorial about how to fix that problem in Windows Mail with a registry fix for spelling related items in Windows Mail, but there doesn't seem to be a registry fix posted for WLM: Windows Mail Spell Check - Vista Forums
In attempting to fix the problem, I repaired WLE via Programs and Features and reestablished WLM as the default email program but it did not help. I also verified that spell check is still functioning.