Server constantly crashing when specific user joins

Server crashes when specific user joins.
Deleting player.dat file works, but only for a few minutes.
Deleting scoreboard.dat doesn't work.
Resetting scoreboard does not fix problem.

User entered a single a /clone command before crashes start happening. User did not use a command block for said command.

No clocks were running at the time. This server is hosting a WIP minigame so there are about 20 objectives on this map. However, the problem started a few minutes after entered the aforementioned clone command.

Server ran fine from release of 14w25b until this user joins and then server crashed upon joining. There is more than enough disk space on file.

I have more crash logs if needed.
crash-2014-06_22_22.23.26-server.txt is the original incident report.

Description: Exception ticking world

java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at amt.a(SourceFile:153)
	at amt.a(SourceFile:49)
	at amm.a(SourceFile:397)
	at bad.a(SourceFile:482)
	at ot.a(SourceFile:175)
	at ayv.a(SourceFile:1006)
	at ot.c(SourceFile:104)
	at ot.d(SourceFile:117)
	at alu.b(SourceFile:273)