Oi! I figured it out. The bitfields were seeded by the files in the includes/xml directory. As soon as I removed the following files, everything started working properly again:
- bitfield_ms_imageshack_upload.xml
- bitfield_ms_megaupload_upload.xml
- bitfield_ms_photobucket_upload.xml
Mosh, will you please do us all a favor and update the uninstall script to delete those files?