If your usb adapter loses the network as well, the problem is further up - it's doubtful that the two of them are dud.
While one of them is there, fill in Your own essid in place of <your_essid> below and post the output of
Code:
sudo iwlist wlan0 scan |grep -B6 <your_essid>
And if your wifi device is not wlan0, fix that too.