Beagle BOARD boots up, runs a few minutes and gets a kernel panic

I have some units in the field that have run for years, using the old Beagle BOARD for remote control of a device. Lately, two of them have gotten into a state where they boot up and work fine for 3-5 minutes, and then get a kernel panic.

I don’t have a text file of the log from the serial port, but a screencopy image. The first line when it fails is :
Unable to handle kernel NULL pointer dereference at virtual address 00000000

Internal error: Oops 5 [#1] SMP ARM

Kernel panic - not syncing: Fatal exception in interrupt

Not sure any of the rest of the info is important, but if there is something specific to look at, I can type it in.

The system is Ubuntu 13.04 (GNU/Linux 3.7.10-x13 armv71)

We have to occasionally run an fsck on the SD card, and this has already been done.

Thanks for any light anyone can shed.