I upgraded from Moodle 2.1 to 2.2.3. I lost most of my images. I have been slowly going through and replacing them and have one course completely updated. However, when I try to back up that course I get "Can not read file, either file does not exist or there are permission problems" and the backup fails. I read through the forums and have double-checked everything to do with the moodledata directory. All the permissions seem fine.
Any other ideas?