My Fireface 400 gives me no end of trouble on my Windows 7 64-bit machine. I bring up the Juce audio selector dialog and switch over to ASIO or even WASAPI and although my app keeps playing, all user input to the Juce app stops working. Sometimes the audio glitches, or stops completely. Its a giant pain in the ass.
On the other hand, my laptop with the RealTek on-board audio…works perfectly, using the ASIO4ALL driver. Never have a single problem with it, with Juce, and I can even get it pretty low on latency.
At some point I guess I will reinstall the operating system fresh and try the Fireface 400 driver with nothing else installed and see if I can isolate the issues but right now its a shit show.