A quick fix is to go to the WiFi Adapters screen in Control panel and disable the WiFi Network Adapter. This will clear the issues that you're having.
Go to Start > Run (or press Windows + R ) and type ncpa.cpl. Right click the WiFi device, then select Disable and Enable. Wait a second and then connect to your network and it should work.
A yellow exclamation mark over the network monitor in system tray indicates that no Internet activity is present, although you can be connected to the router just fine.