While I am usually quite strict in reporting the less rosy statistics on the Greek economy, recent statistics being tossed about that suggest the country's external debt has risen to EUR400bn are a little too aggregated for my liking.
The source of this data is the Bank of Greece, and the detailed statistics can be found here.
Gross external debt is, indeed 400bn. But that includes a lot of things that are not public sector liabilities. Read this, note the graph on general government debt below and make up your own mind. Hint: look out for election periods.