Sitecom slight prob.

Have a Sitecom WL-012 USB and a WL-0120 in the lappy - just got from
http://www.vgicomputers.com/acatalog...tecom_319.html

set up was very easy, the lappy can see the network - and has shared
broadband access -
kids love the MSN messenger bit, however when i try to d/l anything, it
will go 3 or 4 %
then drop the connection ?

likewise if i browse the network for too long - it says "wireless connection
unavailable" even when sitting right in front of it.

Not too sure where to start looking - is there a short term answer like
additional software "like connection keeper on the old dial up service".

both main pc and lappy have XP Pro, both almost new systems to good spec.
have additional wired network all ok, and broadband via Set top box into
Belkin USB adapter.

any clues where to start looking pls ?

thanks
BD