serial console hangs

I have a HP Visualize C200 running hpux that I am trying to boot into using a null modem through com1 from my Sun Ultra 10. I get all the way to the login prompt and then it becomes innactive and wont let me access the machine anymore. Any ideas?

My guess would be a bad null modem cable. You only have data flowing out of the HP but not in. The data travel on different wires in each direction.

Try a similar problem described here.

Problem there was the client terminal emulator, not the cable.