I'm getting the following error message when I click signup

I'm getting the following error message when I click signup on one of my paid memberships. This does not show up with the free membership.

Warning: sprintf() [function.sprintf]: Too few arguments in /home/a2webs/public_html/smshp.org/wp-content/plugins/protected-content/app/model/class-ms-model-membership_relationship.php on line 1093