RRAS problem

We have Win NT 4.0 server have LAN and ISDN adapter on the server , connected two LAN together by using ISDN adapter no Problem when we use the RAS all my connection were successed . When upgrading my RAS to the RRAS we have blue screen from the computer we dail and some times from the computer recieve the dail.
some truobleshooting we tried:
we used sp4.0 and later version
we install all the card from begining
after installition of the card we reinstall the RRAS and sp4.0.
Please try to help me.
Greate thanks to those Who trying to help.