The attached file should replace admin/GT/SQL/Tree.pm and fixes the problem. All users using the above-mentioned databases should replace this file as soon as possible to prevent display problems and/or fatal errors. Note that this file requires Gossamer Forum 1.1.4 and will not work with earlier versions of Gossamer Forum.
The following query will fix any broken threads that already exist due to this bug. It is easiest to enter this query in the SQL Monitor (Admin panel -> Tools -> SQL Monitor), although you may need to change the "gforum_" prefix if you installed with a different prefix.
UPDATE gforum_Post SET post_depth = 0 WHERE post_depth < 0
After running the query, you'll get output something like:
Rows affected: 3
This is the number of threads that had the problem and have been fixed. After replacing the GT/SQL/Tree.pm file and run the above query, you shouldn't see this problem again.