I bought an Alesis MultiMix 8 USB mixer/soundcard. It's a decent little mixer, but I mainly bought it as an external soundcard to help my poor little laptop with GPO. So far, I've only used it in conjunction with playback through a notation program. Works great in that regard.
Then I bought an Alesis Photon25 USB keyboard/controller. I plugged it in, and it worked like a charm, giving me fantastic control that I couldn't match through just notation, but without the external soundcard, my computer chokes.
I plugged in the Photon, and tried it through the Kontakt player. It worked. Then I plugged in the mixer, but a signal only came out of the computer speakers. When the mixer is plugged in, sound is only supposed to go through it, and that's exactly what it does with every other program. I unplugged the mixer, then tried the Photon again. Nothing. I restarted, and then it played. I wanted access to GPO's reverb, so I tried the Photon through GPO. Nothing. And after that, the Photon won't work with Kontakt anymore either, after restarts, plugging in the Photon before or after starting the computer or the program, or any combination/order I can think of.
I'm at wit's end, and would really, really appreciate any help.
Until someone who has your specific hardware chimes in (I have neither) I have a few thoughts that might (or might not) be useful:
1. usb bandwidth--do you have other usb hardware plugged in or do the two devices have high bandwidth requirements? I don't remember how to determine this, I got some information with respect to it by poking around in the control panel (the device manager I think).
2. the other possibility that jumps to mind is driver conflicts. The manufacturers support forum might have some discussion about it if this is the case.
3. something totally different.
Running into these sorts of problems when wanting to make music is incredibly frustrating (I know very well).