Player.dat of one player got resettet when server was terminated (power loss, hard reset)

We had this bug 2 times:
in one of the snapshot (between 1.3 and 1.4) and now in 1.4.4 pre.

After logging on of a player his inventory AND enderchest ist empty. Meens that his player.dat got resettet.
This happend with two different people on our server. (vanilla)

I sadly dont know why. We had some issues with our server before: logging in took to long. But this should not interfere with this bug?