You are using a Surge protector, right?
It is possible that before the power goes off it surges, or increases in voltages, amperages, wattage or even Hertz (Frequency) which causes some damage which requires a reboot to reset the system. The Computer is the most delicate micro-electric (Meaning uses micro measurements of volts, amps and watts) contraption in daily use. Everything inside of it can be damages or knocked off keel with the slightest of power surges, or drops, or even changes in the hertz.
You may be using a $25.00 Power bar, they usually have a reset switch, 6 plug ins and are about 9 inches long with another 18 inches of power cord. These are great if you live in an area with "clean" power - meaning rarely has blackouts, surges, etc.
However it sounds like you live in an area where power is an iffy thing So you may need a more expensive one that is more durable than your power bar.
Monster appears to be a good product. We use their product for our TV/Entertainment center and our Computer system. Both are over 2 years old (We just paid off the Computer and still have another year to go on the TV/Entertainment center) and have had very few problems - I believe it is mostly due to the fact that we are using heavy-duty surge protectors.
Specifically we use
http://www.monstercable.com/power/productPagePower.asp?pin=1884Why? Because it also provides a place for phone line and cable - We are on Cable broadband and cable for the TV.
Our TV before the use was full of "snow", we also are on the outside loop of several circuits here. Not only are our powerlines from TID (Turlock Irrigation District) Older than Dirt, but the power line from the street to the house was installed in the early 60's, the buried power line from the house to the trailer (Nowadays called a Prefabricated Home

) where we live was installed in the early 60's, it goes through 3 breaker boxes before reaching the outlets. With the Rolling Black outs and the small fact that they won't stop building more houses without upgrading the power supply out here, we have some serious surges, mini-outages and other not to nice things like "Brownouts" where everything grows dim.
Our previous computer (Compaq running Win98) lasted almost 2 years. When talking to the Gateway Experts who took the time to ask lots of questions about our needs and what kind of power we get, we were pretty much informed that many of our problems stemmed from our lack of proper protection when it came to power surges.
Using one of these may go a long way at solving the problem you are having.
David