I've recently encountered a bug with Entourage 2004 where, when you attach two different files to an email message and send it, the receiver sees it as two copies of the same file.
So, if I send Alice a message with the files 'foo.doc' and 'bar.doc' attached, she receives the message with the files 'foo.doc' and 'foo.doc' attached. Trying to open either one will open foo.doc. However in my Sent Items folder the message shows 'foo.doc' and 'bar.doc' as it should. Strangely file sizes appear to be preserved, so if foo.doc is 20k and bar.doc is 30k, in the message as it appears for Alice the first foo.doc will be 20k and the second will be 30k. This makes me suspect that it's just some off-by-one error in the array of file names, but it doesn't happen all the time so it's hard to say.
Has anyone run into/fixed this problem before?