SUN Fire V880 server hang

I've installed Sun Ray server software 1.3 and UPS (APC) software on solaris 8 at SUN Fire V880 server. My problem is why the server become unstable. Hang about 3 or 4 times a week and need to reboot. Do I need to install update patches for sun ray server software or it's because misconfiguration of UPS software. Another thing is, if i reboot the server why it hang at boot.

[392 byte] By [eijjan] at [2007-11-25 23:18:35]
# 1
When you say hang, elaborate..... is it at run level 1? when you reboot does it go to run level S?display your error in here?
danzak1 at 2007-7-5 18:06:55 > top of Java-index,General,Talk to the Sysop...
# 2
I don't know the problem, the server suddenly hang.I don't have any idea why the problem occurred. It happened frequently. It ussually happened when student using Sun Ray appliances.
eijjan at 2007-7-5 18:06:55 > top of Java-index,General,Talk to the Sysop...