I had the same issue, but with my issue was the filedata in database was someone how deleted.Lucky i had backups and it was just as simple and as to restore it.

That's what happens with this bug, is that the filedata, and filecontent, get deleted. You were lucky and had a backup to go back to.

--------------- Added [DATE]1442848959[/DATE] at [TIME]1442848959[/TIME] ---------------

You'd want to run a script that goes through each non-zero refcount filedata and looks in the corresponding table(s) to determine the actual usage count for the filedata.

I tried to post a bit of sample code but vb.org kept hanging when I hit post.

first step:

uncomment /includes/cron/cleanup2.php
2) restore a old DB in a testforum
3) search for all entrys where the attachments was assigned a post with this query:

SELECT * FROM post a, attachment b, filedata c WHERE c.refcount =0 AND a.postid = b.contentid AND b.filedataid = c.filedataid

3) Update the refcount value from 0 to 1.
4) Search for the newest IDs from the tables (testforum):
-post
-attachment
-filedata
-thread

5) Search for the IDs (in acutal DB) bigger (>) than the IDs from testforum in:
-post
-attachment
-filedata
-thread

6) export the "new" entrys (bigger (>) than newest ids from testforum) from these tables.

8) Import the new entrys in testforum.

then you have all the entrys from old database and new database mixed and the right refcount value.

9) export the mixed tables
-post
-attachment
-filedata
-thread
from testforum

10) import it to actual db.
11) upload all deleted files in your filesystem


BACKUP FIRST, IF SOMETHING WENT WRONG!

The above is not complete as it will only check post attachments. There are other content types that can be stored in the filedata table which might be where the filedata is actually being used. Albums are one that comes to mind, but potentially any mod you have that allows uploads might have added a new content type.