Checklist:
Tools > Email Accounts > View or Change existing Email Accounts
Check if your both email accounts are listed there.
If not: sure you know what to do.
If there: remove the account and try recreating again.
If this doesn't fix the problem:
Start Outlook XP using another user (Log off and log in as another user -- assuming you are using Windows 2000/XP)
Do the same above.
If the problem stilll persists
