when vaccum hopper is destroyed, it'll create a "ghost" vaccum hopper
it "sucks" things into where the vaccum hopper used to be, but because it's a ghost one, so it starts where it dropped, and repeat the path
placing block into where the hopper used to be doesnt work

This sounds like client-server desynchronization, which usually isn't problem with our mod.
Anyway, your report is terribly incomplete, so please answer following questions:

• What version of OpenBlocks and OpenModsLib?
• Can you reproduce it with OpenBlocks only?
• Does block re-appear after reconnect or server restart?
• Was it on Bukkit/Cauldron/Spigot etc. server?

I think, he will not answer anymore. xD