That's strange. Can you tell us what is your OS ? Take a look at the system logs, they may have some more info. Have you tried rebooting the machine ? I've solved such stubs with reboot, when I'm unable to identify the root cause. Also, is this a single user mode, or normal runlevel 3 ? I guess it's runlevel 3, check with "who -r" and try to change the pass in single user mode.
i am using OS solaris9 /05 hw update and installed on E2900 1.8 GHz.
its the only solaris that supports the post solaris and applications that i will install afterwords (its complicated) why i used this version.
regarding the other info you asked me for i will check for it tomorrow and get back to you.
If you are facing the above problem just go into the single user mode & then modify the shadow file where the encrepted password for the root is placed then give passwd command & proceed as you doing earlier your problem will be resolved.