Broadcom BCM57781 Onboard LAN Keeps Dropping Out And Then Coming Back

I have the above brand of LAN on a ASROCK Z68 Extreme 4 Mobo.Router: Netgear DG834G The whole computer is about 7 months old and as per another recent thread it has a fresh install of Windows 7 64bit Pro. However since the reinstall an issue that also existed before continues to annoy me.Namely, the internet at times drops in and out over a period of hours and then just works.CAT 5 Cable has been replaced and tested in another machine and is fine.There is another laptop, older Dell with Vista on the network (wired) that has no issues, everytime my PC drops I check it and 9 times out of 10 its still working.Whilst I prefer Firefox, i normally solve the issue by opening Explorer and using its Diagnose tool. Quite often it will say ' The default gateway is not available' One bit of info, it also continously says I am on a ' Unidentified network' and ' Public Network' despite it being a simple home wired (NO wifi i switched it off) LAN. How do you change it back to HOME network? sometimes the Public Network is in blue and you can click it and tell it yet again to be HOME but other times its not in blue or clickable to change.