Solaris 10 - init stops working

I have a really strange issue on Solaris 10 running on v490. I'm running Oracle 10g on the box. Everything runs fine and all of a sudden I get a call from a DBA. I check and none of the Oracle processes are running. They were definitely running after the system booted and nobody stopped them. I try "init 6" to reboot the box to return to a sane state, and init doesn't work. "who -r" reports that it's running in runlevel 6, but the system keeps running as if nothing happened ("init 0" doesn't work either). "shutdown" and "halt" commands work thou. Absolutely no indications of any errors in syslog. Any ideas what may be happening to the system? Any advice will be appreciated!