The earliest signs of this crisis were evident when the Greek government had to adopt several austerity measures, starting in 2008. Greece, which was one of Eurozone's fastest growing economies, was used to running large structural deficits as a matter of course ever since it gained independence from military rule in 1974.
The problem with such massive unchecked government spending was that it soon made a dent in the Eurozone's finances--the Euro was introduced in 2001. The entire region had to bear the burden of Greece's debt, the scale of which was being hidden by the country's government, who employed the services of Goldman Sachs to pull the wool over everyone else's eyes.
Soon, other countries like Ireland, Portugal, Belgium and Spain faced similar crises in light of their running structural deficits as well. Of course, the Greek deficits were by far the most severe of the lot, and they could result in the country being expelled from the Eurozone.
For now, Greek Prime Minister George Papandreou has tendered his resignation. Meanwhile, European leaders are still grappling with the idea of either cutting financial and strategic ties with Greece or imposing severe austerity measures in the country, with such measures drastically affecting living conditions in the indebted nation.
There are even talks of asking China to bail Europe out. This, according to most experts, should be the last resort, as it'll give China unprecedented power in the global economy! However, this could also be the only way that an impending credit crisis could be avoided.