client validation is also applied to the fild causingthe issue..
change:
<input id="Appointment_request_group_Phone" name="Appointment_request_group_Phone" type="text" value="" class="formTextfield_Large" tabindex="5" onblur="WAValidatePN(document.getElementById('AppointmentRequest_Brassy_Default').Appointment_request_group_Phone,'',false,true,'x (xxx) xxx-xxxx',document.getElementById('AppointmentRequest_Brassy_Default').Appointment_request_group_Phone,0,true);"/>
to:
<input id="Appointment_request_group_Phone" name="Appointment_request_group_Phone" type="text" value="" class="formTextfield_Large" tabindex="5" />