Okay, I figured it out with some prodding. Two things were wrong. First I added the 10k resistor as suggested above and it did help. Even with LEDs it was unstable, but that resolved it. However, when connecting the nixie it would count at 60Hz instead. Apparently there is some ripple coming from my 230v PS.
In any case I also found that my 1Hz signal was too weak. After reconfiguring that things are much better.
It is still a little unstable. Everyonce in a while I'll notice a digit staying on for two seconds or maybe skip a digit instead. Every time I start a project like this I wish I had an ocilloscope...
For the record, my nixies are common anode and I know about their current limits. :wink: Although they do look VERY pretty when you over-drive them. Bright orange with a blue halo. :wink: