PC sluggish when connected to domain

I have a WINXP SP1 box connected to a Win2003 domain and when they are in the same building connected through a Local Area Network, the PC runs fine. But once we take the PC to another location in the same city where it is connected through a local cable provider’s connection, the whole system slows to a crawl if we log into the domain account. Log into a local account and the system runs fine. Any ideas?