2008 R2 active directory - wrong user name or password on some users

I have 2008 R2 active directory environment with one physical DC and VMware virtual backup domain.

I got wrong user name  or password on some users including the administrator  when trying to log on to the DC\servers\workstation.

After reinstall the 2 DC's the system worked for a few days and I got the same problem: users got wrong username and password while trying to log on.
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have you checked for virus's
Miguel Angel Perez MuñozCommented:
Check workstations and DC´s time. Differences more than 10 minutes would make users can´t logon.
IT_Group1Author Commented:
Thx, Yes.

Any other ideas?
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If multilanguage environment, keyboard layout could confuse password entries.

Does this problem persists when you reset the password to some simple one like: passworD1234
IT_Group1Author Commented:
Guys come on.
Don't think so simple. we're not kids here :)

Please let's try to get to the bottom of it.

Thank you
I reitterate have you checked for any virus activety it sounds wierd enough so it potentiallyt could be
IT_Group1Author Commented:
Yes, we have
Have you checked if there is any suspecious authentication events logged in the event log?
IT_Group1Author Commented:
Will do, thanks.
Any other ideas?
I do virus checking by a linux boot cd i have seen a few virus's that cannot be removed by a windows av program

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If problem occurs and you reset the password to some simple one like: passworD1234 - will the problem still persist?

Do you have a multilingual environment?
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