Cannot connect NWDS to SAP PI 7.31 sp13 Dual stack

Hi,

I am having trouble connecting the NWDS to a Dual stack SAP PI NW 7.31 sp13. I tested the P4 port using telnet and it connects. But when I try to add the PI system to NWDS I get a popup "The following SAP instance cannot be acceses at present [Host:xxx.xxx.xxx.x,InstanceNr:35]"

I can add other systems such as a portal and our NWDI system. These are pure java though. Is there something unique to a dual stack regarding an NWDS connection?

- bruce