No, not at all, but you can try if you like. I still think that it might be down to the USB lead/antenna/driver.
If your external antenna has gone sick, is your standard antenna somewhere that it is actually going to pick traffic up? Can you see any aircraft in the MyFlights list at all with "Get Flights from Network" unticked? You have got "Process hardware flights" ticked?
I can't see any traffic at Gatwick from where I am close to Heathrow.