Why does my machine give a panic?

[Halid Faith]

I used to use freebsd4.X. I didn't have any problem about it. After I
reinstalled freebsd6.1 my server has started to given a panic. I am sure
that the server's hardware is good.  I ran kgdb on the server as below;

# kgdb kernel.debug /var/crash/vmcore.0
[GDB will not be able to debug user-mode threads: /usr/lib/libthread_db.so:
Undefined symbol "ps_pglobal_lookup"]
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-marcel-freebsd".

Unread portion of the kernel message buffer:
dev = amrd0s1e, block = 1008936, fs = /var
panic: ffs_blkfree: freeing free block
cpuid = 1
Uptime: 1d18h28m28s
Dumping 1023 MB (2 chunks)
  chunk 0: 1MB (159 pages) ... ok
  chunk 1: 1023MB (261886 pages) 1008 992 976 960 944 928 912 896 880 864
848 832 816 800 784 768 752 736 720 704 688 672 656 640 624 608 592 576 560
544 528 512 496 480 464 448 432 416 400 384 368 352 336 320 304 288 272 256
240 224 208 192 176 160 144 128 112 96 80 64 48 32 16

#0  doadump () at pcpu.h:165
165             __asm __volatile("movl %%fs:0,%0" : "=r" (td));


How to get rid off that ?