Posts don't show after updating to 3.0.1

Everything’s been working fine for a while now at https://www.themmnetwork.com/. Then this morning I did the auto update for WordPress 3.0.1, and all the posts on the site showed this error instead:

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘autoblank’ was given in /home/themmn/themmnetwork.com/wp-includes/plugin.php on line 166

Now you won’t see this on the site right now. The funny thing is that posts still show when using other themes, and I reverted back to an older theme for now.

I manually downgraded WordPress back to 3.0, but this didn’t solve the issue. I also tried disabling all of the plugins, since the error indicates an issue with plugin.php, but this did nothing either. It’s possible it is a theme issue, but then the posts should have appeared again after I downgraded. At this point I’m not sure what else to try.

Thank you for any assistance.