Mail message hangs when Send to Recipient via Window

Each time I right click on a word file in Windows Explorer and select Send to Mail Recipient, when I send the message it hangs. Explorer stays operational, as does Outlook. Despite that, it does reach the recipient, and appears in Sent Items. But the message screen itself hangs and stays there till I kill it. I’m using Outlook 2003 SP2, Office Prof 2003 and Windows XP Professional. Problem doesn’t occur with eg .pdf files.