asterisk users - Sep 2005 - DTMF detection problems.

I have an Asterisk box (Fedora Core 2, kernel 2.6.10-1.771_FC2smp)
connected to an E1 (MFC/R2 signaling) through a TE110P Digium card. My
IVR doesn't work because sometimes a single digit is recognized two,
three times and sometimes not. I've already changed "relaxdtmf" to
"yes" as well as "txgain" and "rxgain" in
unicall.conf file but,
unfortunately, without success. My configuration files,
/etc/zaptel.conf and /etc/asterisk/unicall.conf, follow below:

/etc/zaptel.conf
==========# MFC/R2 does not normally use CRC4
span=1,0,0,cas,hdb3
#
cas=1-15:1101
cas=17-31:1101
loadzone = us
#loadzone = us-old
#loadzone=gr
#loadzone=it
#loadzone=fr
#loadzone=de
#loadzone=uk
#loadzone=fi
#loadzone=jp
#loadzone=sp
#loadzone=no
defaultzone=us

/etc/asterisk/unicall.conf
=================callgroup=1
pickupgroup=1
language=br
usecallerid=yes
hidecallerid=no
immediate=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=yes
relaxdtmf=yes
rxgain=-1.0
txgain=-0.9

protocolclass=mfcr2
protocolvariant=br,4,4
protocolend=co
callerid=asreceived

context=voki
group=1
channel=>1-15
channel=>17-31