Category:
Weird annoying error messages that take a lot of your time. By the way I'm installing via TFTP and unpacked the ISO.

Error:
Unable to read package metadata. This may be due to a
missing repodata directory. Please ensure that your
install tree has been correctly generated.

Failure:
repodata/36d33ae6f<mess>-primary.sqlite.bz2 from
anaconda-CentOS-201106060106.x86_64: [Errno 256] No
more mirrors to try.

Solution:
Delete the content of the repository directory. Copy the content of the repository directory from a FTP server with Centos distributions. For example from: ftp://ftp.sh.cvut.cz/centos/6.2/os/x86_64/repodata/