I just uploaded a jpg to your site and it seemed to work fine. Is it wmv that's not working? I tested the earlier code I posted and it worked for me for mpg, wmv, etc. ...maybe a filesize limit issue? I'll try and find a small SFW wmv to test upload to your site. Everything I have is large and...um...racy, shall we say. as for x-empty, if that's a genuine mime type that can be detected, then just add it to the $allowed array. In fact you can add any mime type there, including (I recommend) png.
ok, I found a small family-friendly wmv, but now your site is printing out php parse errors and not even displaying the upload page. I'll try again later.