OK, try a TCP/IP stack reset for windows, I have seen network adapters do funny things and no reason for it.
Do the following: -
Reset your TCP/IP settings in Windows 7
1. Click Start. In the Search programs and files field, type netsh int ip reset resetlog.txt. In the results displayed under Programs, click the netsh int ip reset resetlog link.
Notes:
A window with a black background will appear for a moment and then disappear.
Alternatively, press Windows+R on the keyboard to open the Run window. Type netsh int ip reset resetlog.txt and press Enter.
When you run this command, it'll rewrite your computer's registry keys use for TCP/IP settings. This achieves the same result as removing and reinstalling the protocol.
2. Restart your computer. Click Start, click the arrow next to Shut down and then select Restart.