Sparkcom ADSL router disconnecting from TalkTalk

(Router problems messed up the last post so I've started again - just
in case this looks familiar :-)
Hi all,
Having problems with a Sparkcom 4 port Ethernet ADSL router. (using
Conexant chipset)

Bootcode Version= BC_CX82xxx_4.1.0.28
Firmware=CX82xxx_4.1.0.34
Customer Software version= ARTCX-WPT.042905.00FA
Purchased within the past couple of weeks.


Broadband connection provided through Talk Talk. Followed the setup
instructions and ran the optimiser and can happily surf the net......


However.....
at seemingly random times the PPP session status changes to Not
Connected.


Connection Name PPPoPvc 0
Interface Pvc 0
Mode PPPoA
Status Connected/Not Connected


Doesn't seem to be dependant on usage at the time. I can be in the
middle of something and it will just disconnect.
Disconnect Timeout is set to 0
MRU=1492
MTU=1492
MSS=1432
(all as suggested by the optimiser)


Automatic Reconnect is ticked.


Can anyone offer any suggestions please?


Many thanks


Graeme