Savvy traders have noticed that the valuations of European financial institutions are, shall we say...questionable at this point in time. Being savvy and in the business of making money, they pounced and started making money. Unfortunately, this was noticed by the masses of the slightly less savvy, who also pounced and caused those stocks to decline rather rapidly, thereby pointing out that the European banks are also Emperors of the clothing-optional variety.
The European governments do not like this situation, so they've decided to wish it out of existence by issuing short-selling bans.
Let me know how that works out for you.