Recently, I've noticed that many not-full-sized blocks are popping up as items when I walk too far away. So far, this has happened with rails, powered rails, redstone, redstone torches and levers. Once or twice, I've got back in time to pick up the items, but most of the time they despawn while I'm gone. This is on single player, 1.4.5. My installed mods are one that stops creepers exploding and Xray. Does anyone have a similar experience or fix? I've downloaded an inventory editor to replace items, but itis not a very good solution..

EDIT: It doesn't *seem* to be caused by the mods.