FreeBSD hang

[Ada Wong]

Hi,

My server (freebsd version 5.2.1) hang and need to cold boot after it
runs a period of time. I can only get below error in console:

spin lock shed lock held by 0xcd05ac80 for > 5 seconds
panic: spin lock held too long
cpuid=0;
boot() called on cpu#0

syncing disks, buffers remaining
....panic:pmap_invalidate_page:interrupts disabled
cpuid=0;
boot() called on cpu#0

My server config is :
Memory: 2047MB
CPU: 2 x Intel(R) Xeon(TM) CPU 2.80GHz 

Any advice is appreciated. Thanks