"syscall" crash

[John B. Nagle]

     We aregetting "syscall" panics about once a day, caused somehow by the
pty driver in original 4.1BSD, as modified by 3COM and us.  We have modified
"init" to force hangup at logout by setting the line speed to zero for two seconds, and we have modified the pty driver so that network connections get hung 
up too.  But if the control side of the pty is rapidly opened and closed, 
after a few hundred tries, there is a "syscall" panic.  
     When the panic occurs, an instance of "init" is always the active process.
We aren't able to tell what system call was made last, unfortunately.
Any ideas?