Fatal trap 30: reserved (unknown) fault while in kernel mode

[Ma]

I'm using the newest FreeBSD 6.2-PRERELEASE on our web server (compiled at
last friday, 06-12-15). But it always crashes these days.
The following information displayed on the screen with system crashed.
====================================================
Fatal trap 30: reserved (unknown) fault while in kernel mode
cpuid = 1; apic id = 01
instruction pointer     = 0x20:0xc0b9bed1
stack pointer           = 0x28:0xdc95fcd8
frame pointer           = 0x28:0xdc95fcd8
code segment            = base 0x0, limit oxfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflag         = interrupt enabled, IOPL = 0
current process         = 10 (idle: cpu1)
trap number             = 30
panic: reserved (unknown) fault
cpuid = 1
uptime: 3m52s
ahc0: WARNING no command for scb 79 (cmdcmplt)
QOUTPOS = 235
====================================================
-- 
Ma Jie