I just found out that the host I was using to host whmcs is incompatible with it because they have the default soap client compiled into PHP. WHMCS uses the nusoap library and the default soap client completely breaks WHMCS as soon as you try to process an order with it.
Does anyone know of any stable, reliable web host running linux that is known to be 100% compatible with WHMCS? Need to make a decision quickly. Thanks.