http://www.wired.com/wiredenterprise/20 ... ava-linux/
http://serverfault.com/questions/403732 ... eap-second (see top answer)
Linux: The ntp service which controls the server's time ran into a deadlock (aka infinite loop) when it tries to inject the leap second. Only certain kernel versions were affected.
Java: No clue what it problem was... but... it's Java... ^^
The infinite loop caused the CPUs to run at full load which lead other services on the machine to stall.
Note: The company behind my own machine told today that at the moment of the leap second the power consumption of their DC went up by one megawatt)... yeah... that's really megawatt(!).