Ubuntu 12.04 starts up slowly

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http://askubuntu.com – When I shutdown my laptop and then turn it on, after choosing kernel version in grub menu, appears a dark (but not black; ubuntu-color if you know what I mean) screen, and almost nothing happens, hdd led not flashing. This 'silent' period continues ~3-4 minutes, and then systme boots up fine. This happens only after I shutdown the notebook, if I just reboot it, it boots up quickly. Any ideas? (HowTos)