exim error?

[Jason Majors <jason@kwiqsilver.org>]

I'm using mutt 1.3.27i and exim 3.34-1. When I try to send any mail, local
or remote, using mutt I get this message:
Error sending message, child exited 1 ().

When I use mail on the command line, I get no error, but the mail is never
delivered.
It worked fine until a few days ago. I haven't done any apt-gets or anything
in that time. I copied the exim.conf from another box where it works just
fine and restarted it, but I still get the same error.
I have it set up as an internet site and I have connectivity and DNS access.

I am completely stumped. Any ideas?

Thanks,
Jason