Local area connection doesnt have a valid ip configuration windows 7 fix

Hello,
Keep getting this error using the onboard ethernet on new Asrock z77 pro 3 mobo - Windows 7 home premium 32 bit. It worked well for a week or two and then started dropping out. Ive tried a lot of fixed ive seen in posts but to no avail. The router is connected to ADSL2 and all my other devices connect smoothly to internet.
Love some help here:
Ive tried disable/enable many times
Tried to disable IPV6 (not sure if that worked
Stopped Bonjour
Stopped Windows firewall

Any ideas appreciated