[yummyfajitas]

If the Greeks produce X euros worth of goods/serviecs and consume Y euros for Y < X, this should be a minor problem at best - paperwork, really. The actual problem is that Greece can't pay for their current levels of consumption. They haven't been able to pay for consumption in quite a while actually, but previously EU lending propped them up.

This is why Argentina's default wasn't anywhere near as bad - they were fairly close to consuming as much as they produced.

Unlike Greece, Argentina also instituted necessary reforms - for example, import substitution and breaking sticky wages via a 13% nominal wage cut for govt workers and pensioners [1]. Greece has steadfastly refused to do these things in spite of having ample time.

[1] Recall why Keynesians promote inflation - to inflate away real wages, which this cut also did.