I assume you have a IIsi-
I have experienced the symptoms you describe.

I fixed it by :
1. turning on the serial port in /etc/ttys
	modem port is tty00
	printer port is tty01

2. turning off everything else.  
console should be off
ttye0 should be off.

I also had trouble because I managed to cpin 
/etc/ttys with all the \n characters changed
to \r (newlines->carriage returns)
Marc Parmet's port of Emacs did this automatically
and I didn't realize it.

If I boot single-user I have serial console checked
If I boot multi-user I have only serial-echo checked

hope that helps
-Daniel Risacher


>>>>> "Jim" == Jim Ravan <Jim_Ravan@avid.com> writes:

    Jim> I hooked up a serial terminal to the modem port last night
    Jim> and checked the serial console option in the Booter. Lots of
    Jim> the correct text comes out on the terminal when I boot so I'm
    Jim> pretty sure I have the hardware problems solved (thanks to
    Jim> killourh, Steve Allen, and a null modem adapter). But at the
    Jim> point where the login process takes control from init (at
    Jim> least I assume that's what happens), the kernel panics and
    Jim> the debugger comes up. Also input to the debugger is *very*
    Jim> eratic, that is, it's hard to type and have anything echo and
    Jim> be read.

    Jim> So I assume I may have something wrong with /etc/ttys or some
    Jim> such config file. To check out the problem I need to know
    Jim> which serial port, i.e., the modem or the printer port, is
    Jim> mapped to which tty device. Can anyone tell me what the
    Jim> serial port-to-ttyNN mapping is? Is the modem port tty00?
    Jim> tty01? tty02? ...? And what tty dev is the printer port
    Jim> mapped to?

    Jim> And if you are currently using a serial console, please tell
    Jim> me what you did to get it to work. I'm so close to actually
    Jim> *using* MacBSD, I can taste it.

    Jim> thanks for any help, -jim