Laptop shutdown. I have a travelmate 7510, the screen goes black and does not respond, on some

Question

I have a travelmate 7510, the screen goes black and does not respond, on some occassions the laptop shuts down, there is no pattern to this. I thought this was a heat problem and cleaned all air intakes etc. I am running core temp, core 0 53c and core 1 49c. Help needed.Many thanks