Is the file extension .wmv or something else eddie? That's possibly the problem. If it is a .wmv file and it's under 10MB you shouldn't be having problem. Just keep a close eye on the message you get when it looks like the attachment has completed uploading. Often there is a message saying that it has been unsuccessful and the reason why. That's in the small window. Also, you might want to make sure you don't close that small window until uploading is complete. That will cause an unsuccessful upload as well.
Also, if you haven't read this, it may make things clearer. -
Not sure how to upload a music file. Read this.
Let me know if you are still having problems.
Clancy
"I like work: it fascinates me. I can sit and look at it for hours". Jerome K. Jerome