Anyway, if running locally the scripts on the servers give wanted results, so LDAP is working.
You also may have another possibility than a conflict with the udp port : get a look to policies on the server, maybe something is wrong here and don't allow external request. Try with lower security settings, and if it's works, try to strenghten them until you reach the "not authorized" point.
Also, as Les said, you should really do some other test with another computer/laptop and another account