What happened was that I switched (apparently too fast) from Multiplayer to DAG.
It's not a game-stopper, since you can just click on DAG again, after which it works fine.
But this has never happened in 1.3.5.
Easily reproduced, all you have to do is click DAG before the Multi-player unit has logged off.
Lars
Vista Home SP2, nVidia GForce 8600GT (v. 8.17.12.5896) running at 1680x1050