...Spain, Portugal, Italy, Greece.
Of these, Italy is the AIG. The largest of the four in terms of population and GDP. Greece would be akin to Lehman, since it appears its government debt is the catalyst.
If the EU does not, or cannot, guarantee a sizable portion of the liabilities of these countries, this will get very ugly very quickly.
As I have said, many strategists consider a return of Realpolitik (up to and including the point of armed conflict) such a remote possibility that contemplating risk scenarios of what a fractured Europe would look like is a colossal waste of time, and instead focus on Taiwan and the Asia arena.
I am of a different opinion on the subject and advise to refrain from entering into an entirely new point on the risk spectrum. The developed world, sans North America, is to be avoided.