Quoting William R. Dickson (wrd@awenet.com):
> I do have read/write permission (I'm running it as root, I assume I should
> be able to read/write anything I want).

Unless some process opened it exclusively.
Itīs not really useful if two processes open a
device and try to read the same data and both
receive garbage.

> Does this inspire any more ideas?

Didnīt you say you're running some getty on that line ?
I haven't tried with NetBSD so far but the other systems
I know have two device entries for a port, so one can be
blocked by getty but the otherīs still available for
dialout (and some internal code of the driver knows to
put the getty asleep and wake it up after the call is done).

With FreeBSD I've got /dev/tty01 and /dev/cuaa0.  With the
old Ultrix system on my DECstation it was similar and the
real difference between /dev/tty0 and /dev/cua0 was some
bit set on cua0īs minor number.  This told the driver to
override the process that opened the same device w/o that
bit set. (like tty0 is 4,0 and cua0 is 4,128).

HTH,
				Ripley