MarketPress product pages showing errors on Ultimatum Theme

Hi Crew – Please help with this issue that just began with all product pages on my websites using Ultimatum Themes with the latest WPMU Marketpress updates:

Warning: call_user_func_array() []: First argument is expected to be a valid callback, ‘ultimatum_fixes_forMP’ was given in /home/content/…/wp-includes/plugin.php on line 505

I tried finding a solution in the ultimatum forum without luck. The product pages do not show the errors with other Themes so I believe that MarketPress is not playing well with Ultimatum somewhere in the coding.

Your urgent assistance in resolving this will be most appreciated. Please Help.