The only report I have found similar is MC-7134 but this was back in 1.4.2.

However, I was on my friends server and last night silver fish spawned out of the blue and ate the bricks. all I did was use stone bricks (in creative mode) used to make a building. They immediately spawned and devoured the entire building.

All three of us watched this happen and tried out best to kill them. However, We got totally swamped with them. Please release an immediate bug release because I dont know how many people is effected with this on his server.

PV