I'm having a problem with slip...

  Config:
    -	NetBSD/i386, 386sx25, 8Megs ram, 1 serial card, 1 ether card
	operating as a gateway between the slip connection and the 
	ethernet.
    -	The other end of the slip link is an Annex-3 terminal server.


  What happens:

    -	Slip link is established and works for a short period of time
	(We have had it work for several hours ...)

    -	When the slip link quits working (pinging the other end of
	the slip link looses all the packets) slattach can not be
	killed.  It never quits even thought the E flag is on in ps(1).

    -	The link quits faster if routed is run with "-s" instead of
	"-q".

    -	We have tried at least two different serial cards.

Has anyone had this happen?  Any clues as to what is wrong?

Thanks,
--Phil