I've managed to use both 2 USB to GPIB converters (NI GPIB-USB-B) at the same time. They appear in MAX as GPIB0 and GPIB1. I'm using Windows XP and MAX 3.1.
I have tried inserting them
while Labview is running, and the second device just hangs while the the VIs using the first one carry on unaffected.
I can install both while MAX is running without any problems.
Tim Norris
"...and all this science I don't understand
it's just my job five days a week"
Using 6i, 7.0 & 7.1 on Win'98, 2K & XP