when our vpn clients connect the dns settings change and when they disconnect the dns setting do not got back to the original, dns is set to wrong setting and prevents network communication

I have tried opening port 1433 on a vpn concentrator and also a pix 506e but ti does not work. i have made all the rules on the concentrator and added the lines to the access lists on pix still nothing. what did i miss

Anybody else seen this problem we are working with Nera radios newer version of T1 wic does not connect older versions do