Essentially countries in the Euro have been trying to solve their fiscal crisis through deflation (i.e. austerity policies / cutting government spending). In the case of Greece, only when deflating the economy has proved to be a complete failure are they having to realise default is the only viable option left.
The problem for the Euro members is that they are trying to solve the fiscal crisis through deflation alone.
In the case of Iceland, the crisis was accompanied by a substantial devaluation. The UK and US have also seen a devaluation in exchange rate which has made deflation more palatable.