Snow Leopard joined to domain - Odd login

We have several mac's joined to our domain, both Snow Leopard and Lion. We have a tech with admin rights in our AD that can't log into Snow Leopard macs joined to the domain. He can log into Lion machines joined to the domain, pc's joined to domain, but not Snow Leopards. All other techs can log into Snow Leopard using their network account except him. We thought it was computer specific, but we have another Snow Leopard machine (joined to the domain) that won't allow him to log in either. We changed his password in AD and Lion recognized the change and allowed him to log in, but Snow Leopard just shakes it as if it is a bad password. Any ideas? It sounds to be Snow Leopard specific bc his account is fine in AD.