I saw a strange one with FC2T3 while rebuilding a kernel on a Armada M700 laptop.
* use ssh to login with two separate sessions (normal user acct). * use "su -" to become root on both sessions.
In one case the first 'su -' worked fine, but the second session would abort the 'su -' command after the first char of the root password was entered. I was unable to 'su -' a second session over ssh and had to use the laptop keyboard/display instead.
ron