I had a somewhat similar problem recently with an MM2000 Motion
Controller. It even showed up on the NI GPIB Communicator list but
wouldn't talk to me at all. I went over to the instrument panel and
accessed the gpib address setting on it and saw that it was still set
correctly, but for some reason it wouldn't work until I essentially
reconfirmed it as the address. After that communication went fine. So
you might try re-entering the address. Other than that I'm not really
sure what other things there are to try. I'm a bit new to this myself
but have had that problem before.
