SUID process disables modem logins. Why?

[Quentin Fennessy]

I am running an HP 835 with HP-UX 3.1.  I also have INFORMIX TURBO
running.  Turbo is a setuid-to-root program.  My company has to maintain
a copy of this program and an application in a remote site, which we
presently do over a 1200 baud dialup.

My problem is:  If Informix-Turbo is started up on a dialup login,
the dialup port will not work until Turbo is killed or the machine
is rebooted. (Same thing)

Scenario:  login at 1200
	   tbmode -k	| Kill turbo
	   do misc work
	   tbinit	| start Turbo
	   ^D

	   At this point, I can no longer access this port over the phone
	   line.  There is a getty running, and I have sent HUP to init
	   to reset it, to no avail.  When we dial up, we can see the modem 
	   lights flickering.

What is happening here?  I am stumped.  Unfortunately we are in a production
environment, so I can not bring Turbo up and down all the time for debugging.
I will be visiting the site soon, and hope to have some answers by then.

All suggestions will be appreciated.  Email and I will summarize.

Quentin Fennessy