LinuxQuestions.org - system crashes time to time

Hello All,

I have a problem:

The Debian Sarge system crashes time to time.
First of all Nautilus dissapears panels stop working trying to "ctrl+alt+beckspace" to reboot the X server stops the server and it does not come up.
When I try to log in via text console (cntrl+alt+f1-6) it refuses to login sowing message
"tty respawning too fast" or something like that.
I can't either login via ssh/telnet.
Trying ctrl+alt+del in text console tells it can't execure /sbin/shutdown

However system still responds on keyboard and I still connect via this computer to internet (it shares the internet to other PC at home)

Only hot reset can be done. :cry:

The system under external+internal firewall.
Kernel 2.6.12-1-386.

Example of typical last mesages in log before the crash (but they are instant messages and heppen all the time) after crash untill reboot nothing in logs.

Code:

# grep 'Nov 15 14:23' /var/log/syslog

Nov 15 14:23:31 localhost kernel: ATTACKIN=eth0 OUT= MAC= SRC=10.0.0.1 DST=10.255.255.255 LEN=78 TOS=0x00 PREC=0x00 TTL=64 ID=528 DF PROTO=UDP SPT=137 DPT=137 LEN=58

Nov 15 14:23:33 localhost kernel: ATTACKIN=eth0 OUT= MAC= SRC=10.0.0.1 DST=10.255.255.255 LEN=78 TOS=0x00 PREC=0x00 TTL=64 ID=530 DF PROTO=UDP SPT=137 DPT=137 LEN=58

Nov 15 14:23:33 localhost kernel: ATTACKIN=eth0 OUT= MAC= SRC=10.0.0.1 DST=10.255.255.255 LEN=78 TOS=0x00 PREC=0x00 TTL=64 ID=532 DF PROTO=UDP SPT=137 DPT=137 LEN=58

Nov 15 14:23:35 localhost kernel: ATTACKIN=eth0 OUT= MAC= SRC=10.0.0.1 DST=10.255.255.255 LEN=78 TOS=0x00 PREC=0x00 TTL=64 ID=534 DF PROTO=UDP SPT=137 DPT=137 LEN=58

Nov 15 14:23:35 localhost kernel: ATTACKIN=eth0 OUT= MAC= SRC=10.0.0.1 DST=10.255.255.255 LEN=211 TOS=0x00 PREC=0x00 TTL=64 ID=100 DF PROTO=UDP SPT=138 DPT=138 LEN=191

Nov 15 14:23:39 localhost kernel: parport0: FIFO is stuck

Nov 15 14:23:39 localhost kernel: parport0: BUSY timeout (1) in compat_write_block_pio 



# grep 'Nov 15 07:12' /var/log/syslog

Nov 15 07:12:17 localhost kernel: parport0: FIFO is stuck

Nov 15 07:12:17 localhost kernel: parport0: BUSY timeout (1) in compat_write_block_pio

How can I degug the problem and find the problem.

HW:
I've runned memtest86 for several hours, also all seems fine.
What is the direction to explore the problem