Description of problem:

I have a firewall with latest kernel-2.6.18. running after 7-9 days ,kernel hangs with message
CPU 0 Unable to handle kernel paging request at virtual address 00000004, epc == c018c1dc, ra == c018c18c
Oops[#1]:
Cpu 0
$ 0   : 00000000 cfffffff c0190000 fffffffe
$ 4   : 00000003 00000002 81456870 c0000000
$ 8   : 00000018 00000008 8067fb80 00000006
$12   : 0d5edd10 00000000 00000001 00000000
$16   : c0191ee0 00000000 8067fb80 00000000
$20   : 00000000 00000000 c0000000 c0191ee0
$24   : 00000000 80220000                  
$28   : 8067c000 8067f9e8 c018b510 c018c18c
Hi    : 00000000
Lo    : 00000000
epc   : c018c1dc decode_seq+0xcc/0x4c8 [ip_conntrack_h323]     Not tainted
ra    : c018c18c decode_seq+0x7c/0x4c8 [ip_conntrack_h323]
Status: 1000c403    KERNEL EXL IE 
Cause : 10002008
BadVA : 00000004
PrId  : 00006303
Modules linked in: antiattack xt_multiport xt_state nfnetlink_queue nfnetlink_log ip_queue ip_nat_tftp ip_nat_snmp_basic ip_nat_sip ip_nat_pptp ip_nat_irc ip_nat_h323 ip_nat_ftp ip_conntrack_tftp ip_conntrack_sip ip_conntrack_proto_sctp ip_conntrack_pptp ip_conntrack_netlink ip_conntrack_netbios_ns ip_conntrack_irc ip_conntrack_h323 ip_conntrack_ftp iptable_nat ip_nat ip_conntrack iptable_mangle iptable_filter nfnetlink
Process swapper (pid: 0, threadinfo=8067c000, task=80680000)
Stack : 00000000 190011bb ae3bd052 00000000 00000000 00000000 c0191ee0 8067fb80
        00000000 8067fb80 00000005 00000001 00000000 c0192834 c018b510 c018cb94
        63b46072 81860000 8b73bd00 00000006 c0191e68 c0191e50 00000000 8067fb80
        00002add c018c894 8b73bd00 00000000 00000000 80257620 c019296c c0191e50
        8067fb80 00000001 00000000 00000000 80000000 c0191dd8 c018b510 c018c320
        ...
Call Trace:
[<c018c1dc>] decode_seq+0xcc/0x4c8 [ip_conntrack_h323]
[<c018cb94>] decode_choice+0x248/0x2d8 [ip_conntrack_h323]
[<c018c894>] decode_seqof+0x2bc/0x374 [ip_conntrack_h323]
[<c018c320>] decode_seq+0x210/0x4c8 [ip_conntrack_h323]
[<c018c320>] decode_seq+0x210/0x4c8 [ip_conntrack_h323]
[<c018c320>] decode_seq+0x210/0x4c8 [ip_conntrack_h323]
[<c018cb94>] decode_choice+0x248/0x2d8 [ip_conntrack_h323]
[<c018cc70>] DecodeRasMessage+0x4c/0x64 [ip_conntrack_h323]
[<c018a528>] ras_help+0xec/0x1000 [ip_conntrack_h323]
[<c005cc30>] ip_conntrack_help+0x50/0x98 [ip_conntrack]
[<8055c6d0>] nf_iterate+0xac/0x11c
[<8055c7dc>] nf_hook_slow+0x9c/0x1c8
[<8056ebb0>] ip_output+0x224/0x424
[<8056b094>] ip_forward+0x240/0x35c
[<80568c9c>] ip_rcv+0x360/0x7c4
[<8053fe40>] netif_receive_skb+0x358/0x52c
[<804668f8>] e100_poll+0x1f0/0x6bc
[<80540418>] net_rx_action+0xd4/0x2b8
[<802340c0>] __do_softirq+0x9c/0x14c
[<8023420c>] do_softirq+0x9c/0xc8
[<80204354>] do_IRQ+0x24/0x40
[<802015c0>] plat_irq_dispatch+0xd0/0x1f0
[<80202620>] ret_from_irq+0x0/0x10


Code: 02a2102b  10400025  2631000c <96230004> 30620001  14400024  24020001  30620010  1440fff1 
Kernel panic - not syncing: Fatal exception in interrupt