I have this problem too but manifested in a different way. In my case being able to select the Player tab for unit 192.168.1.122 seems to hinge upon having previously selected Listen mode.

This is trio.xml when it has broken:
<unit mode="Queue 'n Play" layout="universal" access="protected"/>
<unit ip="192.168.1.121"/>
<unit ip="192.168.1.120"/>
<unit ip="192.168.1.122" mode="Listen"/>

If I select Queue n Play on the actual receiver, I can then select the Player tab.

This is the state of trio.xml thereafter:
<unit mode="Queue 'n Play" layout="universal" access="protected"/>
<unit ip="192.168.1.121"/>
<unit ip="192.168.1.120"/>
<unit ip="192.168.1.122" mode="Queue 'n Play"/>

I hope that helps, and I would be happy to do further testing, or testing of a patch.

Setup is W2K, ARM 1.04 and tRio.

Many thanks again

M