Connection contains real IP of NATed address

I was receiving this error in Checkpoint firewall log when using the Cisco IP communicator on the VPN Client pc. The symptons were that although I could hear the other party, I could place calls but the other party could not hear me. I resolved the issue by adding a NAT rule in Checkpoint as follows

Original Packet
source=any
destination= (ip address or range of vpn client)
Translated Packet
Source = original
destination= original
service= original