I have had several instances where redstone wires and powered blocks will randomly disappear from my SSP world. (Started earlier than 1.4.4)
Sometimes, when I interact with them the components will drop as items;
i.e. walking up to an iron door with pressure plates on either side, stepping on one plate caused the door and both attached plates to drop as items.
Other times when I log in, they have simply vanished, i.e. redstone wire attached to dispensers in my chicken farm and the attached buttons are no longer present when I go into the room where they once were (also, a TNT cannon of mine loses all redstone wire/repeaters/torches/nearby trapdoor).
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This originally occurred in vanilla Minecraft back in the 1.2's, although I have added mods since then (Modloader, Forge, Shelves, Armour Stand, Pet Bat)
Can you check if this occurs on 1.4.4 or 1.4.5 without any mods?
Happens on a MODDED client with X-Ray mod(on triggering)
Can you reproduce this in vanilla minecraft?