asterisk users - May 2005 - DTMF asterisk-2-asterisk using SIP w/ dtmfmode=rfc2833

Hi,
I'm am getting doubled DTMF on some digits with one of my providers
who also uses asterisk.  We're using SIP, with dtmfmode set to
rfc2833, and the codec G.711.
Once out of every five or ten calls, there are no problems, but more
often than not, the DTMF is getting doubled-up on at least one of the
digits of the extension dialed.
I've tested with a CVS-HEAD from Febuary, and just now reproduced it
with a fresh install (CVS-HEAD-05/16/05-20:22:32).
I've used ethereal to capture the RTP stream and cannot see anything
wrong with the 'RTP EVENT' packets -- whether my asterisk box sees the
correct extension or not, the RTP EVENTs look okay as far as I can
tell.   There's no evidence of the DTMF being doubled before getting
to my box.

Has anyone else encountered this problem and found a solution?
If the RTP EVENTs are good, where should I be looking for the problem?

Thanks in advance for any help... 

Kinda stumped,

-Gary