The problem for me was a conflict between the SimCoders software for the DHC-2 Beaver and the particular way Brunner uses datarefs. SimCoders worked out a solution for this, and it’s now working brilliantly.
A tip for that disconnecting in XP:
Go into the settings menu in CLS2Sim and check the “Auto connect” box little more than halfway down the settings page, in the middle. That way the software will autoconnect if you loose connection for whatever reason. I find that I loose connection when I enter the menu of X-Plane, so I make sure to not have to do that in the middle of a maneuver. 😛