SOLVED: Ok, a Dlink support rep let me know how to fix it. The cause was the SP2 upgrade. You have to log into the PSTN gateway (http://xxx.xxx.xxx.xxx:9999, default password admin) and then click on System at the top of the page and click on Restart on the left. Select Restart with Factory defaults and restart the gateway. Next, access the Response Point admin and remove the voice service (adaptor-gateway) and add it again. Worked like a charm. I suggested that this should be somewhere in the firmware upgrade instructions somewhere.