Forum error: Upload failed due to failure writing temporary file.
 

I recently assisted a site with an upgrade to vBulletin 4.2 PL3. Since the upgrade, any attempt to attach images results in the error: error: Upload failed due to failure writing temporary file. The permissions on both the attachments folder and the tmp folder and on all subfolders therein are CHMOD 0777. The directory into which attachments are being stored is ./attachments

Any help on what might be causing the issue would be greatly appreciated.