Vista - vista ent net use problem

i found that i can't use net use command to map lpt1 in vista ent version,
but i can map lpt2.
anyone know what is the problem in vista ent? i test in vista business, i
can map lpt1 and lpt2.
in vista ent, when i type "net use lpt1 \\server\printer"
it needs me to enter user name and pasword, however i tried all user still
can't map.
however, i type "net use lpt2 \\server\printer" , it is susscess to map.
anyone have this problem?
pls help~~~~ thx a lot~~~