This is looking like a System Controller (SC) problem. Why is the clock saying year 2000? Perhaps the CMOS battery has died??
Certainly, if the SPARC box asks the SC for the date/time and the result is way prior to the date/time that it's running with that will surely confuse the hell out of the system!!
http://docs.oracle.com/cd/E19076-01/...ntMessage.html
Is the system under an Oracle hardware support contract?
---------- Post updated at 04:48 PM ---------- Previous update was at 04:21 PM ----------
You said that you had tried a STOP-A on the Sun keyboard with no result.
STOP-N should reset the OBP parameters (if they are corrupted). Maybe worth a shot.