cannot access network

In our branch office, we connect directly to another location in order to access our data entry applications. We are running XP pro on 6 machines, and we must map a networked drive before launching the application, but when we go to map the remote drive, we always get the message “the referenced account is locked out and may not be logged onto” When we put in a call to them, they apparently unlock the account or reset the password, and then its ok. The machines have static Ip addresses and are connected to a hub and in turn to a router with a T1 line. Are we doing something wrong? because it only started occuring a few weeks ago.