Ok, here is the situation as I see it now. System has been working fine for months. Made a few changes recently including installing sp1 and then later sp1a. I have been having trouble with server published ports suddenly stopping with no error messages etc. I have narrowed this down to only our 2 DNS servers having trouble. It is the UDP mapping which is failing, the TCP mapping stays fine, as does all other published ports. Netstat -an still says these ports are connected even though they have stopped working. Now this is failing in less than an hour on restarting the system. I have tried uninstalling the sp and reinstalling it, to no affect. I noticed in the logs that the UDP queries for these ip's were being blocked. Do you need to setup packet filters as well as server publishing these ports ? Anyone got any ideas how to proceed ? I am not local to this machine at the moment, but will be in 8 hours time. I will try uninstalling ISA and reinstalling if no one has a better idea. Patrick