How to use encypted home directory after reinstallation

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http://askubuntu.com – I reinstalled Ubuntu on a machine with encrypted home directories. After that installation I have edited the fstab to boot the old home partition in /home. After doing so I can not login anymore with LDM. If I type my password, witch is the same as before, after a short moment of activity I am referred back to login page. I think this is due to the fact, that my home directory is not decrypted correctly. But I read here that this should work. What am I supposed to do? (HowTos)