Is it Outlook, or Outlook Express?

Do exactly what Stijn said: toss mail, empty the trash. Make sure you don't have a bunch of draft messages trying to attach this doc. Shutdown Outlook. Empty Windows trash. Shutdown (not restart) your computer.

Test send a message to yourself.

Then open a message, try to attach a <b>different</b> document.

If you're still having problems Alex, give me a call.

Dave