asterisk users - May 2005 - DTMF problems with International Calls

Folks,

I've setup an IVR system that's been running fine (in production) for
the last 6 months. It's primarily been used for North American calls.
The problem I'm having is that for international calls, DTMF does not
work. The tones just don't get detected. I tried a number of different
codecs and options, but to no avail. I'm using IAX through my
provider.

The numbers that are known not to work are: 

+48605xxxxxx
+61405xxxxxx (OTOH, +61299xxxxxx works fine)
+48508xxxxxx

I've confirmed that the +61405xxxxxx number is a GSM cell phone in
Australia (does not work), and the +61299xxxxxx is a landline (works
fine).

So... has anybody seen these issues before? If so, are they any workarounds?

Thanks,
Mohit.

-- 
Mohit Muthanna [mohit (at) muthanna (uhuh) com]
"There are 10 types of people. Those who understand binary, and those
who don't."

What should the description be for a digium FXS card when running the 
lspci -b? Mine shows the following.



00:09.0 Communication controller: Tiger Jet Network Inc. Tiger3XX Modem/ISDN 
interface
        Subsystem: Unknown device b100:0003
        Flags: bus master, medium devsel, latency 32, IRQ 10
        I/O ports at ec00 [size=256]
        Memory at dffff000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [40] Power Management version 2




Thanks,


Gary