In snapshot 14w04b there was a fix that made spawners load into the world properly. With lack of spawners in my world I tried to test this. I loaded a copy of my world (as well as my world to be sure) and found that x-ray machines didn't work. I reverted to 1.7.4 and went into my survival world; the items in the chunks that were loaded (thankfully not my storage room) had no items in them. One of the furnaces was even on without anything to smelt.
Dowgrading is and was never supported
MC-45009