sorry for bad english, I'm Brazilian.
I created in the snapshot 14w08a teleport systems relative to entities using WitherSkulls with custom UUID (1-1-1-1-1, for example).
To teleport to these entities, I used "/ tp @p 1-1-1-1-1", and worked well. After 14w10c update, is no longer possible teleport or interact with these entities, actually kill them is not possible. using "/ kill @e" all entities in the world are killed, but not WitherSkulls. The message "That entity can not be found" is shown, but if I use the command "/say @e" they appear in the list, with their respectives UUIDs.

commands:

/summon WitherSkull ~ ~ ~

/kill 1-1-1-1-1 (Show "That entity can not be found")
/tp 1-1-1-1-1 (Show "That entity can not be found")