Hi,
it's been a long time, since you posted this thread. We had the same problem and after days figuring out what's going wrong, we found it out:
The filenames where reserved names, e.g. activities.png or viewgroup.png. Both files where 100KB each and one could see them in moddata of the course and in moodledata.
Finally we suggested to change the names, e.g. to activities-2.png and viewgroup-2.png, and upload the newly named file. Suprisingly the files showed up!
Now our problems is, deleting the old files. We deleted them in moddata but the links still show up in the attachment-page even though the files aren't in the Moodle-system anymore.
I have two questions:
1. Where do I get a list of reserved names/words in Moodle?
2. How do I get rid of the filenames in the attachment-page? I quess these links are somewahre in the database.
We're using Moodle Version 1.9.8.
Cheers,
Monica