asterisk users - May 2006 - Linksys spa 942 handsfree SIP->PSTN/GSM

Customer has approx 20 internal extensions (x-lite, 4
ananlog phones using spa 2100) all these phones have no problem. e.g.
using speakerphone on an analog phone calling to PSTN is good quality.

Only the 942 speakerphone is giving us voice quality problems:

SIP to GSM/PSTN calls with speakerphone:  extremely choppy.  call is
uniteligible

SIP to SIP internal calls with speakerphone:  good

SIP to SIP internal calls with handset:  good

SIP to GSM/PSTN calls with handset:  good

Spa942 has factory conf.  

Thanks in advance for any advice provided.

Melisa.