10.04 Lock-up/sudden shutdown (not overheating)

[mrchumpley]

For the last 24 hours my computer has started locking-up or suddenly shutting down not long after booting up.

I run Lucid 10.04 and it has been regularly updated. The computer is 5 years old and has GeoForce motherboard with dual core 64 bit processors; 4GB RAM; two 500GB SATA drives.

Sometimes I can get as far as logging in and getting onto the internet, but sometimes it locks out at the log in page.

When I boot and run from a CD (as now) it is fine. I've checked processor temps and they're both fine. The only odd thing is that when I boot from CD it says that an unrecoverable error occured during installation and it will have to start a desktop session, which it duly does.

I've run disk checks and they all seem to be un-corrupted.

I have two questions:

1. Any ideas about how I could go about investigating this and fixing it?

2. How do I copy files to back them up from a desktop session? Every time I try to copy the Home folder it tells me I don't have permissions, even though I have given myself Administrator rights.

Many thanks in advance.

MrC