We've uncovered an odd situation when uploading excel documents. We use the "accept" attribute to limit uploaded content to excel documents only and it works according to adobe documentation except when the document being uploaded is open in excel. If you upload a document that is currently open in excel it changes the mime type to application/octet-stream. If you close excel and upload the exact same document the mime type is application/vnd.ms-excel.
Interestingly enough this only seems to be a problem in IE. If I run the same process in Firefox it doesn't change the mime type on upload. Is anyone else experiencing this problem. How did you deal with it?