The web interface to the PEAR bug tracker allows us to upload .patch and .diff files. It checks for the Content-type of the uploaded file and rejects everything that's not a text file.
I tried uploading my patches many times and always got rejected - when using my beloved Opera browser. It worked with Firefox and Konqueror, though. Yesterday I finally took the time to find out why this happened. Started up my favorite network traffic sniffing tool, Wireshark, and uploaded a patch.
The second HTTP POST packet told me why I got rejected: Opera sends the file with type application/octet-stream, apparently because it does not use my system's MIME database and doesn't contain the information about diff files itself. So I opened Preferences, Advanced, Downloads and added a new MIME type text/x-diff for .diff files - and uploading patches to pearbug works like a charm.