After I installed the Windows Live Writer beta 3, I noticed that the spell checker didn’t work anymore. The reason was the fact that WLW was localized to Finland. However I only write English text so I’ll need the English dictionary. Hopefully the WLW team will let users to choose the spell check language directly from the WLW in the future.

Currently you can fix this issue by changing the loc file. That file seems to only have a ISO 639-1 language code (codes here). By changing the code to en, WLW enables the spell checker.

Default loc file path is:
C:\Program Files\Windows Live\Writer\loc