Hi Cheryl,
Doing the following should fix our problem. Add $mime = strtok($mime, '; '); below both $mime = exec("file -bi '$f'"); (line 160) and $mime = shell_exec("file -bi '$f'"); (line 164).
This is a minor bug, which will be fixed in the next release. Essentially, some servers add the charset value at the end of the mimetype, and this is what throws off the detection.
If this doesn't solve it, then it is the case in which the server is not executing the UNIX file command. This usually happens with some shared hosting plans. There is nothing I can do about that. The best thing for you to do in that case is to upgrade your PHP version to 5.3+ so that it can use the fileinfo functions. See http://www.php.net/manual/en/function.finfo-file.php
Hope this helps. Let me know how it turns out.