As reported by Jarrod Holder in http://moodle.org/mod/forum/discuss.php?d=169588
Updated a play site from 1.9.10 to 2.0.2. Trying to run the Blog visibility update that's recommended and I get the following error:
Notice: Undefined property: stdClass::$message in /mysite/mod/forum/lib.php on line 4113
Followed by "Error writing to database"