Took PC World 5 months to accept that there was a problem!
Finally identified it as either RAM or the connection from the RAM to mainboard that was causing the problem.
Sometimes froze after 5 minutes....when PC World tried it they ran a programme for three days and it never froze once....when they stopped the programme it promptly froze!
Don't know how you check it but thats what happened to me.
Hope you get it sorted soon (remember the frustration)