JomSocial issue (I think) - Joomla! Forum - community, help and support

i'm getting warning , fatal error on website worked fine until jomsocial update. now, error whenever tries register new account. happens within member sign-up , virtuemart store.

here's error:

warning: call_user_func_array() expects parameter 1 valid callback, class 'communitymodelgroups' not have method 'addmemberscount' in /home/larchmon/public_html/components/com_community/libraries/core.php on line 1252

fatal error: call undefined method communitymodelgroups::addwallcount() in /home/larchmon/public_html/components/com_community/models/groups.php on line 85

i'm running joomla 1.5.26
and jomsocial 2.6.2

anyone have ideas on how fix this?