In 5 minutes after join to multiplayer server, blocks changed it's texture to random pixels or sometimes to weird pattern (about 80% of pixels was transparent). I had situation when textures turned "rave mode", and changed in about halt of second it's graphic. I putted ZIP package with some screens from this minecraft while this bug happend.
As you can see on screens, bug do not affected chests or signs. In some places texture of block changed to nether portal texture.

Sorry for bad English.