Another bit of information:

In my Trio.xml, I have this as my Rio RPC call:
http://192.168.0.5:8080/jrec_serv/servlet/RPC2

and in my Jreceiver.properties.xml, I have:
rio-rpc=http://192.168.0.5:8080/servlet/RIO-RPC2

Standardizing on the Jreceiver one throws an exception in Trio, and standardizing on the Trio one doesn't change anything.

Hmmm...

-Dan