I might have some more info and be closer to the soloution.
I am still getting the problem but I think it is down to SDL.
I did a fresh install, installed firefox, rebooted and it was fine.
I then installed VLC which uses SDL and rebooted. Bang, it was dead.
So this time I reinstalled the ROM and just installed the SDL files. It died again on a reboot.
On another note, I have also reized my partition to 121Mb
Anyone got any further ideas?