No DNS Resolution

Have NT 4 network (sp6a) have 1 pdc and 2 bdcs. Have exch 5.5 sp4 server, proxy 2.0 (w2k) and web server (w2k sp1) that all have dual nics. Am connected to full T-1 that comes in through a Ascend Pipeline 130 router. In the last day I have lost the ability to resolve outbound dns names. Our provider has tested the inbound T-1 and all is working to the nic in the servers. I can ping out by ip number but when I try to ping www.name.com I get either a time out or bad ip address response. From the outside my web server works fine. All inbound and outbound email has stopped. Any thing I have missed aside from changing out the router? Thanks Jeff