asterisk users - Apr 2011 - Problems with woomera (ISDN BRI) and playback app: Dropping incompatible voice frame

Hi, when I receive a call from ISDN BRI (with a Sangoma A500) and I try
to playback something I get the following error:

**[WOOMERA]** HW DTMF supported s1c1-
    -- Executing [number at from-pstn:1] Answer("WOOMERA/g1/1-7b29",
"") in
new stack
**[WOOMERA]** +++ANSWER WOOMERA/g1/1-7b29
   -- Executing [number at from-pstn:2] Playback("WOOMERA/g1/1-7b29",
"pbx-invalid") in new stack
**[WOOMERA]** +++SETOPT WOOMERA/g1/1-7b29
    -- <WOOMERA/g1/1-7b29> Playing 'pbx-invalid.gsm' (language
'it')
[Apr  6 19:12:18] NOTICE[1434]: channel.c:4046 __ast_read: Dropping
incompatible voice frame on WOOMERA/g1/1-7b29 of format alaw since our
native format has changed to 0x2 (gsm)

I don't have this problem when I receive calls from PSTN (Sangoma A200).

Can someone help me?

Darkbasic