Yes, thats what i meant by in parallel with the 5v regulator. I have them both running straight off the power supply and I get similar results.
The thing is though, the nixie tube works fine off the 750ma power supply, as long as i get the 5v somewhere else. So i found a 1.6A power supply, and I still have the same problem, even though more than twice as much amperage is available. I thought this was weird because obviously the nixie tube is getting enough power from 750ma, which leaves more than 750ma more available for everything else. Is this an incorrect assumption?