Bukkit

What is the problem?
If there is a rail on a block, then the block that the rail is on is destroyed by being hit, the rail gets destroyed because there is nothing under it.
When this is rolled back, only the block that was destroyed is rolled back, not the rail that was on the block.

(I didn't test this, but this probably applies to pressure plates, switches, buttons, etc.)

This also happens with sand and gravel.