The Euro has been shown to be a big mistake, and I'm glad that Sweden isn't part of it (even though younger me voted in favor of it way back when). A significant portion of Greece's problems come from not having their own currency, or rather that those problems would be much easier to solve with their own.*rimshot*
I was talking how the Euro and the lifting of trade barriers let them sell more of their goods to the rest of Europe.
Normally, when nations differ in productivity and such, this will be reflected in the value of their currency. This makes their exports cheaper and imports more expensive, which stimulates the local economy. Currency fluctuations is a much smoother way of handling that kind of thing than renegotiating wages would be. But now, Greece has to use the same currency as Germany while having nowhere near the same productivity (Germany's GDP per capita is about twice that of Greece), which leaves them completely unable to compete.
In addition, there are many economists who say that Greece has been completely mishandled from the start of the crisis. When your economy is contracting, austerity measures are pretty much the worst way of handling things. Greece's economy has contracted by about 25% since 2007. Certainly, things needed to be done to deal with the widespread tax evasion and mismanagement in Greece, but the heavy-handed cutting of social services, pensions, and the like has only contributed to the crisis. It's like telling someone with weight problems and lung cancer at a hospital that he needs to go on a starvation diet while on chemotherapy - that will just reduce his ability to deal with the more urgent problem. Once the cancer is dealt with, sure, then a diet would be good, but first things first.
Of course, this is massively simplified, but it does give an overview of the problem.