The flight to safety is reaching fever pitch again.

(Bloomberg) -- Treasury one-month bill rates turned negative for the first time in 10 months, as issuance declines while investors seek the most easily-traded securities amid a renewal of risk aversion.
The rate on the four-week security dropped to negative 0.0101 percent, the lowest since it reached negative 0.015 percent on March 26. The Treasury sold $10 billion of four-week bills on Jan. 26 at a rate of zero percent, the second auction of the securities in three weeks at zero percent. Winning bidders will receive no interest on their investment.

Why is this happening? What are the markets afraid of?
The one word answer is - Greece.

Credit-default swaps on Greek sovereign debt surged to a record on concern the government won’t be able to plug the largest deficit in the European Union, a day after it priced 8 billion euros ($11 billion) of bonds.
Contracts on Greece soared 48 basis points to 373, according to CMA DataVision. Swaps on Spain rose 17 basis points to 127, Portugal climbed 18.5 to 149 and Italy was up 10 basis points at 114, CMA prices show.
...
“Who’s going to lend money to them next time and at what price?” said Gary Jenkins, head of credit strategy at Evolution Securities Ltd. “What’s happening is very negative and could lead to a vicious circle.”
The yield on the Greek 10-year bond rose 44 basis points to 6.68 percent as of 4:35 p.m. in Athens, with the difference in yield, or spread, against German bunds increasing by 46 basis points to 350 basis points, the widest since December 1998.

I guess Greece's debt auction last week doesn't really matter after all.