Outlook opens Word, instead of sending emails

Hello,
I'm having a problem with Entourage (XP). I can download emails, but then whenever I try to reply from Entourage, it tells me that there is a problem, won't send, and then tries to recover a fantasy document in Microsoft Word when I close the Entourage doc. Now, I can only send emails from my webmail. I've downloaded all updates from Microsoft, and send in the error message about a dozen times. No luck. Doesn't anyone have any idea how to deal with this?
Many thanks -
Jay