Error Message OG Forum

I'm running Drupal 5.7

When I try to add a new forum topic, I get the following error messages, please advise:

* warning: reset() [function.reset]: Passed variable is not an array or object in /home/teamdiet/public_html/modules/og_forum/og_forum.module on line 712.
* warning: key() [function.key]: Passed variable is not an array or object in /home/teamdiet/public_html/modules/og_forum/og_forum.module on line 713.
* warning: array_key_exists() [function.array-key-exists]: The first argument should be either a string or an integer in /home/teamdiet/public_html/modules/og_forum/og_forum.module on line 714.