I installed W7 RC on two machines for testing purposes. On one I had the yellow exclamation mark but not on the other. Tried the suggestion to turn off Windows Update, but that didn't work. Someone had suggested to disable and then enable the network adapter. I tried and it worked! Now I have the Network Icon showing I have Internet My internet goes through a proxy server! Before I tried this I was wondering why there wasn't any response from MS on this issue. Concluded it must be a bug.

I've been there too.Apply this and you don't have to disable and enable your network adapter: To resolve this issue, disable the DHCP BROADCAST flag in Windows Vista. To do this, follow these steps: Click Start, type regedit in the Start Search box, and then click regedit in the Programs list. Collapse this imageExpand this image If you are prompted for an administrator password or for confirmation, type your password, or click Continue . Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUID} In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network. On the Edit menu, point to New , and then click DWORD (32-bit) Value . In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER. Right-click DhcpConnEnableBcastFlagToggle , and then click Modify . In the Value data box, type 1, and then click OK . Close Registry Editor. By setting this registry key to 1, Windows Vista will first try to obtain an IP address by using the BROADCAST flag in DHCP Discover packets. If that fails, it will try to obtain an IP address without using the BROADCAST flag in DHCP Discover packets. It worked for me since yesterday.