Appointment selection error

Hello, when I select a service, search for time slot, then select a provider and search for time slot, I have this error message... how can I fix this ?

[Appointments+] You have at least one javascript error on http://mydomain.com/make-an-appointment/?wcalendar=1346522724&app_provider_id=1&app_service_id=2.
Error message: Uncaught ReferenceError: Invalid left-hand side in assignment
File: http://mydomain.com/make-an-appointment/?wcalendar=1346522724&app_provider_id=1&app_service_id=2
Line: 230