How many network adaptors do you have installed? You should have only three: your modem, your NIC, and DUN as a logical adaptor. I beleive NT has the option of setting one adaptor as "primary". Usually the primary adaptor is the that is used to connect to the Internet (i.e. your modem). Your system would query the modem first, and then the NIC, when connecting to the local network. This would cause a slowdown.