Hi,
Well, it sounds like something you need a 40 node test network for :)
I was wondering whether it was some kind of MAC bug that was being triggered because of so many units say, overflowing the keycache or something. But if it's software encryption then maybe not. I wish I could help more, but setting up a 40 node network to test is a big challenge. :)
Is it a gradual thing? Ie, do you know when it starts to hang? Does it hang at 40? or gradually as you approach 40?
As for association limits - I thought there was a maximum station parameter somewhere...
-adrian