asterisk users - Nov 2004 - ZyXEL 2000w unregistering and no audio

Hi all,
I'm trying to get a ZyXEL 2000w (with newest firmware) working with our 
in-office Asterisk 1.0 server.  We have other SIP phones working.  I've 
set up the Zyxel using the web interface and having it using g711ulaw 
compression.  The first call after restarting the phone seems to work 
great.  After that, however, things go down hill.  The phone randomly 
starts saying "Unregistered", and will still dial but will not play
any
audio, or send any audio (the line picking up a call from the 2000w 
doesn't hear anything).

Is anyone else having this problem, or has anyone fixed this problem?

Thanks,
Chris

-- 
Chris TenHarmsel
Software Journeyman
Atomic Object, LLC