For whatever reason, IE 7 can report the first part of the UA string as "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ;" at times. Notice both IE 6 and 7 mentioned. When it does this, the uploader popup is shifted to the bottom of the browser window and part of it is hidden.
I can reproduce this by setting the UA string in Firefox to "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; .NET CLR 1.1.4322; .NET CLR 2.0.50727)" as an example.
Attached screenshot was taken using the Firefox method.