The system just uses iptables for nat and there is often these error as follow:
Apr 2 13:27:20 debian kernel: Unable to handle kernel paging request at virtual address 00040030
Apr 2 13:27:20 debian kernel: printing eip:
Apr 2 13:27:20 debian kernel: c0168a15
Apr 2 13:27:20 debian kernel: *pde = 00000000
Apr 2 13:27:20 debian kernel: Oops: 0000 [#1]
Apr 2 13:27:20 debian kernel: PREEMPT
Apr 2 13:27:20 debian kernel: Modules linked in: ipt_REJECT ipt_limit ip_nat_ftp ip_conntrack_ftp ipt_state iptable_nat iptable_filter ip_conntrack ip_tables ipv6 parport_pc parport floppy pcspkr 8139cp pci_hotplug via_agp uhci_hcd usbcore 8139too mii agpgart tsdev mousedev evdev capability commoncap psmouse ide_cd cdrom genrtc ext3 jbd ide_generic via82cxxx ide_disk ide_core unix font vesafb cfbcopyarea cfbimgblt cfbfillrect
Apr 2 13:27:20 debian kernel: CPU: 0
Apr 2 13:27:20 debian kernel: EIP: 0060:[dqput+13/320] Not tainted
Apr 2 13:27:20 debian kernel: EFLAGS: 00010206 (2.6.8-2-386)
Apr 2 13:27:20 debian kernel: EIP is at dqput+0xd/0x140
Apr 2 13:27:20 debian kernel: eax: 00040000 ebx: 00040000 ecx: c10b24bc edx: c3bf8000
Apr 2 13:27:20 debian kernel: esi: c14e47d4 edi: 00000037 ebp: c028e38c esp: c3bf9e94
Apr 2 13:27:20 debian kernel: ds: 007b es: 007b ss: 0068
Apr 2 13:27:20 debian kernel: Process kswapd0 (pid: 43, threadinfo=c3bf8000 task=c395cb70)
Apr 2 13:27:20 debian kernel: Stack: 00000000 c016946b 00040000 c08fe2cc c14e47d4 c48883d4 c14e47d4 c14e47d4
Apr 2 13:27:20 debian kernel: c3bf9eec c01594f1 c14e47d4 c14e47d4 c0159581 c14e47d4 c3bf8000 c3dfd294
Apr 2 13:27:20 debian kernel: c3dfd29c c015991c c3bf9eec 00000000 00000080 00000080 c14e499c c143f99c
Apr 2 13:27:20 debian kernel: Call Trace:
Apr 2 13:27:20 debian kernel: [dquot_drop+41/80] dquot_drop+0x29/0x50
Apr 2 13:27:20 debian kernel: [__crc_bus_remove_file+2833633/6068597] ext3_dquot_drop+0x1f/0x3a [ext3]
Apr 2 13:27:20 debian kernel: [clear_inode+132/201] clear_inode+0x84/0xc9
Apr 2 13:27:20 debian kernel: [dispose_list+75/128] dispose_list+0x4b/0x80
Apr 2 13:27:20 debian kernel: [prune_icache+410/471] prune_icache+0x19a/0x1d7
Apr 2 13:27:20 debian kernel: [shrink_icache_memory+24/48] shrink_icache_memory+0x18/0x30
Apr 2 13:27:20 debian kernel: [shrink_slab+238/332] shrink_slab+0xee/0x14c
Apr 2 13:27:20 debian kernel: [balance_pgdat+380/559] balance_pgdat+0x17c/0x22f
Apr 2 13:27:20 debian kernel: [kswapd+193/197] kswapd+0xc1/0xc5
Apr 2 13:27:20 debian kernel: [autoremove_wake_function+0/58] autoremove_wake_function+0x0/0x3a
Apr 2 13:27:20 debian kernel: [ret_from_fork+6/20] ret_from_fork+0x6/0x14
Apr 2 13:27:20 debian kernel: [autoremove_wake_function+0/58] autoremove_wake_function+0x0/0x3a
Apr 2 13:27:20 debian kernel: [kswapd+0/197] kswapd+0x0/0xc5
Apr 2 13:27:20 debian kernel: [autoremove_wake_function+0/58] autoremove_wake_function+0x0/0x3a
Apr 2 13:27:20 debian kernel: [ret_from_fork+6/20] ret_from_fork+0x6/0x14
Apr 2 13:27:20 debian kernel: [autoremove_wake_function+0/58] autoremove_wake_function+0x0/0x3a
Apr 2 13:27:20 debian kernel: [kswapd+0/197] kswapd+0x0/0xc5
Apr 2 13:27:20 debian kernel: [kernel_thread_helper+5/11] kernel_thread_helper+0x5/0xb
Apr 2 13:27:20 debian kernel: Code: 8b 43 30 85 c0 75 36 68 00 29 26 c0 e8 42 07 fb ff ff 73 40
Intel Celeron (Mendocino) 400M RAM 64M