N300 PR2000 Trek won't connect to internet-connected DM111P modem by Ethernet

Hi, I recently bought a Netgear N300 travel router (PR2000, Trek).

I wish to use it to set up a wifi link at home between my laptop and the Netgear DM111P cabled modem through which I connect to the internet. I will only be using wifi when in other parts of my house than my office. When I'm in my office, which is where all this kit resides, I connect my laptop to the modem using an Ethernet cable. So I'll be switching the Ethernet cable from the modem back and forth between laptop and router quite a lot.

The N300 travel router worked when I first got it a few days ago, but now its "internet" light fails to light up. My laptop connects with the router OK using wifi; it's just the Ethernet connection between the router and the modem that I can't get to function.

Should I return the router to the retailer, or is there some way of fixing the problem I should try first? The firmware is version 1.0.0.13. I downloaded 1.0.0.14 but was unable to upload it to the router. I'm using Win7Pro.

Advice welcome.

Many thanks in advance.

Neil