asterisk users - Nov 2005 - Call progress from sip gsm gateway to pri interface - doesn't get through

Hi,

we have following setup : PBX <-> Parlay <-ISDN PRI-> Asterisk
<-SIP->  GSM
Gateway

Call comes from PBX through Parlay to Asterisk and it routes it over SIP to 
GSM gateway. GSM gateway gives back call progress (it takes some time to 
ring or get through), but this info won't get back to Parlay on ISDN PRI 
interface (Digium PRI card), so Parlay after some timeout disconnects 
call....

We guess that this setup should work, but we're not sure. Anyone with 
working setup like this? Anyone with experience of call progress getting 
from SIP to PRI or BRI interfaces ?  Any advice or pointer to more info ?

Thanks in advance,

regards,

Rob.