After numerous rounds of: “We don't even know if Osama is still alive,” Osama himself decided to send George Bush a letter in his own handwriting to let him know he was still in the game.
Bush opened the letter and it appeared to contain a coded message: 370HSSV-0773H

Bush was baffled, so he e-mailed it to Condi Rice. Condi and her aides had no clue either, so they sent it to the F B I. No one could solve it so it went to the C I A, then to NSA.

With no clue as to its meaning, they eventually asked Britain's MI-6 for help. MI-6 cabled the White House:

“Tell the President he's holding the message upside down.”