Help! Canon ImageRunner gives "Out of Paper" error only for certain computers

Hi everybody--ok, this one is driving me nuts. I have a Canon
ImageRunner c3100 on our small office network. Two older computers (one
Win98, one XP) can print to it just fine. However, the two new
computers that I just set up (both XP) don't print right. Whenever I
try to print from either of the new computers, the Canon beeps twice,
then gives the "Out of Paper" error on it's screen, even thought it has
plenty of paper. Since it only happens on the new computers, I know it
has to be some configuration error on my part, I'm just not sure what.
I've used all the same software and drivers, and have checked the
configuration against the older XP computer without seeing any obvious
differences. Any suggestions would be highly appreciated. Thanks, Ken