Thanks for your post regarding doing simultaneous input and output on your USB device. I have created a VI which pretty much does want you specified. If you have any further questions with this then please feel free to post back.
I was having the same problems. I managed to get the input channels working via the sample programs, (progams>National Instruments>NI-DAQmx>examples>labview 7>dynamic). where you have to choose your channels type in "dev1/ai0(1..2..3 whichever channel you're using) rather than clicking on the browse button. I am still having trouble getting the ao programs to work. Peter, I'm interested in the program you posted however I don't have Labview 7.1 only version 7.0, I don't suppose you have a V7.0 compatible version?