The Euro remains robust because the fundamentals of their economy are sound- the balance of payments is neutral to positive, year after year. Debt is internal, so inflationary pressure doesn't affect Euro valuation. And of course dollar holders are attempting to balance their holdings with other currencies, because the dollar is still over valued. The only reason it is is because too many nations hold dollars as reserve. If they can achieve better balance, then dollar devaluation won't hurt at all, because their other holdings will go up proportionately. If the dollar drops 50% against the Euro, and you hold equal value of both in the beginning, you won't lose a thing. If You're the average American Joe, you get screwed hard, because the price of imported goods shoots through the roof... you didn't have any Euros, Yuan, Yen or Swiss Francs before the roof fell in, did you? And you just get paid in yankee dollars, right? Too bad, so sad. Don't worry, though, the American financial elite is now diversified worldwide, so they'll be just fine... maybe even better than ever if they get the timing right of selling the rest of us down the river...
The Greeks are pretty much in a position where they must default or where the other member nations are willing to forgive much of their debt in return for better future behavior. Otherwise, they'll withdraw from the EU, tell German bankers to piss up a rope, issue new drachma, go from there. The situation for the rest of the European debtor nations is less clear.