I have been encountering this problem ever since I download NullDC. I can set up two controllers just fine, but when trying to play games it never works. It will either register both controllers as controller 1, or only register the controller set up on Controller 1 as Controller 1, and it will not register on Controller 2 as Controller 2. A few months ago, I believe I was able to get it to work by emulating one controller as keyboard using Xpadder, and setting up the other as a Controller in NullDC. Since, I have not been able to duplicate that. It clearly supports up to 4 controllers, or else there would not be options for it - at least, if I were to make an emulator for a system that supported a certain amount of controllers, but not all of them worked, I would restrict it to only the number that worked, that's just me though. Anyway, this is really getting on my nerves, does anyone know how to fix this? Next thing I am going to try is to set up both controllers to emulate the keyboard, there is enough buttons to accommodate two, so...
Another problem I have been experiencing is that only Controller 1 will stay plugged in when I exit NullDC. I can have all 4 controllers set up with PuruPuru, but then exit NullDC, run it again and only Controller 1 is set up. This is extremely aggravating, especially when sometimes I go to set up a VMU on one controller, NullDC will crash and I will have to do it all over again.