I've tried #5 again after the reboot. Same thing. It just reboots again.
I have 50.4MB free on the device and about 800MB free on the SD card. I have tried a 512MB card from another manufacturer with the same result. I have also tried copying the sdcard directory to SD on a different machine. I have tried FAT and also FAT32 formatted cards. No joy.
There are no other log files. Should the /tmp directory of the device be empty?
Thanks for your help though.