"NETWORK CHANGE DETECTED" - Broadband dropping out

About 4 to 5 weeks ago I started finding my broadband connection would just 'drop out'.

I'd lose it. No email or internet browsing, nothing.

It might come back on it's own, it might not.

Generally I'd run diagnoistic's, and some time sit would come back immediately, some times I'd have to run it a few times

Sometimes I'd give up and walk away.

Often I get the message "NETWORK CHANGE DETECTED", and the connection would re-establish itself.

It may run for minutes, and I'd be back at square one, or it could run OK for days.

All extremely frustrating.

I've read past posts and see that this problem has come up before, but I cannot find a "do this to fix it" resposnse.

Seeing that it's happened to others, I'm hoping it's something Apple can advise on.

Does anyone know why this happens and how to fix it. I'm really at my wits end.

I've been in contact with my internet provider who give me the usual answers.

Mac-Mini (2.4Ghz Intel Core 2 Duo) running OS 10.6.7

8Gb Ram

Netcomm Modem NB6PLus4W

Broadband ran fine from Late December 2010 until mid may 2011. No idea whats cause this issue.

Thanks all.

Robert