Hardware: system hangs randomly

From NAS-2000.org

If the system may stop from responding:

- no access through network (no response to ping)
- system reboots
- when connected through serial port you may see
  "Unable to handle kernel NULL pointer dereference..."
- other suspicious behaviour

You should try to turn on the built in fan. If the symptoms disappear there is a thermal problem. If you do not like the noise of the fan you could look at the HowTo entry Cooling for RAM, reduce fan noise