Any more news on this? It's definitely an issue lurking in NH somewhere as I'm getting the same issues with 2.1.2GA. I'm ok with a couple of threads but when I ramp up to 8 or so, each with its own session and enabling MARS on my connection string (SQL Server 2008) to try to get round the "open DataReader associated with this Command " issues, NH just starts to collapse with the same sort of bugs James is seeing... and it happens quite quickly too, so it doesn't seem to be a soak test type bug.
I'll see if I can repro via test case too, but it may be tricky which of course makes it even tricker for you guys to fix it! :)
