Of course I don't believe these countries demise is caused by longer working hours. I know Italy a bit more than Greece and the main problem there is decades of widespread corruption at all levels of society.
But in some way it's a small reflection of an inefficient society.
Greece is in a crisis because of the combination of:
a) massive, pervasive tax evasion
b) insane overspending in the public sector.
Or, well, cooking the books.
Also: Knowing what I've learned about Greece the past five years I wouldn't really put much trust in government-collected data on how much they work.