Speedstream 4200 lights no connection

Hi,
I have a speedstream 4200 modem which worked fine until last week but now isn't connecting at all.

As soon as the the power is turned on all lights come on and stay on for approximately 30 seconds then briefly flash off and back on for another 30 seconds or so and this keeps repeating.

It makes no difference if the phone or ethernet cables are plugged in.

I've tried turning off and on, repowering up everything and pushing in the pin reset (once and also holding it in for 30 secs) but to no avail.

Does anyone know what might be wrong? Is it a dead modem? Is there some magic means of resetting which I could try?

Thanks in advance.
Kate