test it on the other USB ports, test it on another comp to see if the usb dongle works, if both are a yes, double check you have the latest w 8 drivers from the net for the correct version of windows (64bit or 32bit) , - what is the model of the USB dongle and your router?, maybe it doesn't support your network ie , does not support N or 5ghz.
I've tested the dongle and done all that you've suggested above.
I'll detail what happens: my laptop will be able to detect the network, but it just won't connect. I've even removed the password and tried to connect, and it still doesn't work. This happens on both the dongle and the on board wifi adapter.