Multivendor Multigateway Payment Installation Problem

I tried to install Multivendor Multigateway Payment, but it gives an error after the installation that reads like:

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'gozabocheckout_ec_settings' was given in /opt/lampp/htdocs/drupal-5.1/includes/form.inc on line 218.

Any hint why the stated callback is invalid or unavailable? And any pointer to the relevant document would be appreciated.