Are you running directly from battery or keeping the ac adapter plugged in? On any portable unit a battery problem will certainly gum things up if it needs a full charge or is not keeping a charge the way it should. The ac adapters generally quit in an instant when going on you.
Besides power issues the next thing would be high temps! Actually that would be the most common problem since most models in use for several hours daily need to be placed on some type of cooling pad for laptops, notebooks to keep the temps down. A friend recently bought a larger faster drive for one that quit since no one was using the cooling pad bought for it. Then the usb power cable was misplaced?
The other thing that can result in drive errors and OS hangs is the need to run the Check Disk tool. You can schedule that for the next startup by way of the Start>Run or command prompt or simply by clicking the Check Now button found in the right click on drive properties screen>Tools tab under error checking.