Your computer may be overheating and the protection circuitry in the bios is turning it off. Very common problem with Toshibas, I found out.I have a Satellite p35-s609 (had it for just over a year) and I have to clean the dust out of it about every 4-6 months to prevent this from happening. Your cooling fans are probably running at or near full speed when this happens. Unfortunatly, the heat sinks are not easily accesable from the bottom like some laptops. To get to them, you would have to gut the entire computer and pull the motherboard out from the top of the machine. To avoid having to do this, or being without a computer for days or weeks while it is serviced, I used a VERY powerful shop vac (the kind that can hold a bowling ball)to pull the dust out of the machine by putting it up to the fan intake grills (stick a toothpick into the grill to keep the fans from turning too fast and possibly damaging them). You can also use compressed air blown into the exhaust vents in conjunction with the vacuum. Do not just blow air into the machine without something to suck it out, it will just get blown deeper into it, possibly causing other problems. Hope this helps. There is a website called notebookforums.com that I go to, they have sections for all brands, including Toshiba. Very helpful place.