asterisk users - Nov 2004 - Strange g729 error. Just now started.

We have been using g729 for over 2 weeks now. Not a single sound file is
stored in g729. Everything is WAV.
The only time the g729 is used is when someone accesses their voicemail.

HOWEVER, for some unknown reason, this came up today:

Nov 17 15:39:13 WARNING[1125327680]: file.c:779 ast_streamfile: Unable to
open cytel/queue-opening (format G729A): No such file or directory

queue-opening is our IVR main menu. We've had hundreds of calls come in and
listen to this file successfully. Now, in this ONE case, I got this error.
I've changed nothing.

Any ideas?

Matthew