Thanks Larry,I regularily use the Twinhan and Nexus-s to record programs at the same time using one instance of Mytheatre. When trying to set it up for the Fusion card, the third device I had all sorts of problems and ended up just installing Mytheatre in another directory to use the Fusion card. All three cards can record at the same time. I think that using separate card(n) profiles, you can have more than 2 cards active with one instance of Mytheatre, but that was quite some time ago so I could be wrong. I just found installing two instances of Mytheatre worked fine for me.
My TwinHan drivers are version 2.4.1.1 (WDM).
I was using the WDM drivers of the same version in MT 3.8, but they won't work in the 4.0 beta, nor will they work in DVBViewer. You need the BDA drivers for those.