You might try this:
1. Check that your clock is adjusted properly. (sounds silly I know but I once found mine on the wrong year)
2. Try deleting the account (restart WLMail) and adding it back.
3. Try changing your password (at account.live.com).
4. Wait a bit longer.
5. Try logging in and out several times repeatedly.
If that don't work, I don't know what else to do.
It might help someone else if you listed your computer specs.