Netmeeting 3.01

I have a remote client using netmeeting 3.01 which connects to my office through an ISA server using gatekeeper. I get the box pop up saying someone is calling accept or reject call. When I click on accept it does not respond back to the remote client to say we are not in a call. All the gatekeeper settings are correct as per doc on isaserver.org and on the remote site the netmeeting ports 1720 and 1503 are open.