Can't get consistent Wireless Connectivity

I have just recently had broadband cable installed at my home and have
been using it without issue. I have now just purchased a Netgear
wireless router/modem (MR814) and plugged it into the modem.

I have been able to successfully connect to the internet and to the
router but it appears that the connection slows to a grinding halt
10-15 seconds after connecting.

I can connect to the routers admin page and I attempt to go through
the set-up wizard but it keeps timing out on the same page about 4-5
steps into the process. Also, when surfing the net, I can view 4-5
pages and then it just stops responding and the page times out.

From what I can ascertain, it appears that most of the time it is when
I am attempting to submit a form and send information over the
internet but this is not hte case everytime.

Can anyone offer any guidance as to where I should be looking or going
to resolve this?

I am a Telstra Bigpond Customer (Australia) and I can disconnect and
reconnect the login to temporarliy regain service again. I can revert
back to the modem and surf the net without a problem.

Please help.

Thanks

Shannon