If your system is trusted and it sounds like it is, you can try the following after you bring the server up in single user mode:
1. cd /tcb/files/auth/r
2. vi the file "root" and delete the line that has the entry u_pwd.
3. Reboot the server into mutiluser mode.
4. Login as root at the console, you will be prompted for a new password.
Some companies that I know of keep a 2nd user on the server with a UID=0. Ofcourse, if you are using sudo, then you can access SAM through and reactivate the root account. That way you do not have to worry about any downtime as a result of rebooting the server.
Cheers,
Joseph.