Checkpoint SecuRemote and MS ISA

I have the need to get Checkpoint Securemote to be able to get through the Microsoft ISA 2000 server to a remote LAN. I have opened the necessary TCP and UDP ports however I am only able to do the Site Update. This did not allow me to connect fully.Checkpoint mentions forwarding ip port 50. Has anybody come across this problem and able to resolve it withing MS ISA 2000?