asterisk users - May 2006 - DTMF Tones within my Asterisk on all type of Channels

Hi,

i am using Asterisk 1.2.6 with Debian Kernel 2.6.8-2-386 and up 2 date
Zaptel, Libpri and so on.

My Hardware :

4 x SNOM 320
One Wildcard TDM40B
3 x Allnet 7950
1 x Fritz!Box  7050 - working as a ATA

I use Asterisk in my Business stable since last year, the problem occurs
since 2 or 3 months.

I have detected some DTMF Tones within my conversations and turned on a
DTMF Logfile to get more infos about this.

The LOG reports Tones - they looks like appearing randomly on any type
of channel (mISDN, ZAP, SIP) and i cant find any reason why.

Here is a part of the LOG :

Apr 13 10:18:59 DTMF[5007] channel.c: SIP/30-1352 : *
Apr 13 10:39:52 DTMF[5165] channel.c: SIP/20-5073 : #
[...]
Apr 15 07:50:53 DTMF[14182] channel.c: Zap/1-1 : A
Apr 15 07:51:44 DTMF[14182] channel.c: Zap/1-1 : A
Apr 15 13:04:36 DTMF[14909] channel.c: SIP/50-7aa2 : 4
Apr 16 20:20:11 DTMF[19677] channel.c: mISDN/1-u61 : 9
[...]
Apr 18 07:33:32 DTMF[26583] channel.c: Zap/1-1 : 5
Apr 18 07:38:50 DTMF[26663] channel.c: SIP/50-21c4 : 9
[...]

As you can see, this happens on any type of available channel, the user
can hear the tone and in the baddest case the "*" appears
and the function to transfer in the DIAL is active (tT)..

Can you give me a tip to get this problem solved or locate it ?

Best Greets from Germany,

Stefan