graphical Bug involving several chunks. i dont really know how to explain this..

What I expected to happen was...:

What actually happened was...:
some chunks were appearing wrong. some parts within the chunks that are affected is shown repeatedly. also some (deformed ) blocks seem to move around randomly within the affected chunks.

Steps to Reproduce:
1. ... I don't know.
2. ...
3. ...

I do not know if the bug has already been reported, but I couln't find it.