I will try to reproduce the problem in CentOS 6.3 in the next days.
Is there anything special on the authentication part of your installation that I should take care of?
Did you have problems on not being able to login?
I was wondering if your original problem comes from a virus changing manually /etc/passwd file and somehow mapping another user to id 0 (instead of root user). I had experienced it myself.
In the other hand the problem might come because Rescatux forces a given method of authentication (SHA1 instead of SHA512).
You might need to edit /etc/passwd manually in the end.
Finally you can try to reset root password again by using a very easy password written as if you had an English keyboard.
I mean, Rescatux does not work with your locale keyboard by default but with US keyboard (It will be fixed in next releases).
adrian15