So I screwed up.  In my zeal to make sure my blogs are fully spell-checked, I added a misspelt word to my Windows Live Writer user dictionary.

There are no easy way (at least, as far as I could tell) to remove it.  I ended up doing the following:

Open in notepad:

%APPDATA%\Windows Live Writer\Dictionaries\userdic.tlx

Fix the spelling, save the text file back.

Restart Windows Live Writer

I hope this helps someone out there.