Files cannot be ingested

I get this message when I upload a file (.jpg and .pdf):

"The file xxx could not be ingested because its media (MIME) type could not be detected."

Please advise!

Check out this post on the same issue (scroll to the bottom):

http://omeka.org/forums/topic/file-upload-failed-mime-type-coulndt-be-deteced-for-jpeg-images