asterisk users - Mar 2005 - What causes this changethread error message?

I'm running Asterisk HEAD from March 4.  I've Googled a bit but I
can't
figure out what causes this error:

app_queue.c:374 in changethread: Can't change device '**Unknown**'
with no
technology!

It doesn't seem to be causing any problems, but I'm curious what causes
it.
I did a few Google searches and found a lot of people asking about it, but
no real answers.

> -----Original Message-----
> From: David Brodbeck [mailto:DavidB@mail.interclean.com]
> I'm running Asterisk HEAD from March 4.  I've Googled a bit 
> but I can't
> figure out what causes this error:
> 
> app_queue.c:374 in changethread: Can't change device 
> '**Unknown**' with no
> technology!
> 
> It doesn't seem to be causing any problems, but I'm curious 
> what causes it.
Never mind.  It was from something I was doing with an external script.