Bug#466741: gnome-screensaver: fails to unlock with correct password

[Ilya Melnikov]

Was the same problem. I can successfully login, but can't unlock
session. Unlock dialog always reports the password is invalid.

The problem was in file permissions. I manually rewrote “/etc/shadow”
from backup after partition restore. As result file permissions
became:
-rw-r----- root root
but must be:
-rw-r----- root shadow
... and unlock dialog didn't accept passwords.

After some hours comparing with working system I understood my
mistake, fix permissions and unlock dialog works fine.

p.s.
May be this post is unnecessary or isn't related to this bug. But
first “googling” brings me to this thread and I didn't find any words
about permissions here. May be this post will be useful for people
with same problem.