Greece joined the eurozone in 2001. In 2002 it seemed they cooked their books to make their country look more profitable on paper and to meet the requirements for entering the eurozone. In 2004 a new a government found the extent of the lies, but the greek olympics were coming up so they didn't say anything. After the olympics they didn't come out with their figures, but tried to fix everything behind the scenes. They might have been able to do it, but in 2008 the global financial crisis hit and Greece got slammed. Their taxation system effectively failed and shut down and their very good social benefit systems just started eating money.

Greece needed money and since they were in the eurozone, if they didn't get it everyone else would suffer. They were bailed out and were trying to turn things around, but it's at this time that investigators of the loaners, who now had official access to the books, uncovered what the greek government had been hiding. Greece's credit rating is downgraded, the cost of borrowing goes up, and the loan conditions kill a lot of cushy jobs and push unemployment through the roof.

Things snowball, Greece borrows more to pay for old debts, but at higher interest rates which just pushes them farther into debt. This spiral goes on for a while and the people get pissed. The books won't balance as people don't have enough money to pay the tax rates required to keep up with even the paired down social services and to pay back the loans.

Now they need money again and the EU is getting sick of taking the government's word that this time things will be different. The EU, specifically Germany, is now saying "alright, we'll give you money but now you have to do things our way." These are harsh measures for greece and would be painful, but Germany has a track record of fiscal responsibility so it's probably got some merit.