I'm having some strange troubles getting dial-up ppp to work reliably.

MacIICX 32M memory 1G disk.  NetBSD 1.3

USR Robotics Courier modem

Bill Studnemund's ppp kit fitted and operating.

Problem is as follows:

First time after booting machine, ppp always works just fine in terms
of connecting and transmitting/receiving data.

Typing  ppp-down  to stop ppp disconnects modem but fails to properly
kill the process, even though it issues the correct kill command.
Repeating three times usually finally kills the process.  This can be
solved by forcing a

kill -9 <process_id>  

but that shouldn't be necessary.

However, the next time I try to run ppp (by typing ppp-up) the modem
hangs; it seems to be getting weird signals from the serial port, as
it indicates on the lamps CTS,RTS,MR,TR,SD,RD all active which is
improbable.

A different 19200bps modem just hangs quietly without flashing lights.

No error message comes back from pppd.

Killing the process and resetting the modem by power-cycling means
that I can get it to work again, but it is a pain to have to do that. 

Two modems, and two cables don't resolve it, and I don't think it is a
problem with the chat script as I have years of practice with chat
scripts for UUCP connections.  I have tried running at lower port
speeds (9600 and 19200) and the problem is entirely repeatable.

Any ideas of where to look?

Thanks.

Russell.