RE: Terrorism - Surely if it were the case an organisation would take responsibility? Otherwise, wouldn't its purpose be defeated?
On radars - Someone mentioned it earlier, but blackspots can produce some pretty heinous conditions. I'm not sure about the 330s radar, but on some of the older 744s i've seen wx literally 'pop' onto the screen within 20nm, being hidden previously by other walls of wx. In areas of exteme activity, i.e. frontal lines, tropical depressios, this could be potentially dangerous, with nowhere to turn...
I hope the investigators can ascertain the cause.