This is a very common problem (google it) effecting win 7 that sadly has many different causes depending on the hardware. I have an esprimo q520 running 7 64 pro, and following a reboot it can't seem to find the internet, using the lan port. Even though it finds the internet fine on wireless, and finds the lan either wired or wireless. My workaround is to pull the Ethernet cable out and reinsert it. This fixes the problem straight away but is far from ideal. Up till now awakening from sleep works fine and it seems to be able to find the internet no problem then.
I have played around with the ethernet power management settings, updated the adapter drivers, disabled and enabled the adapter, all of which have made no difference. I do not have bonjour service running either. Please could you provide me with a fix or a better workaround. Thanks.