This is the photographic documentation from the autopsy I did on my electric hand mixer. The upper right-ish portion shows the gears (plastic, off-white in color), which were completely stripped. The inside smelled like cookie dough (mmmm, cookie dough...) and was lightly coated in a fine powder, which I'm assuming was composed primarily of flour.
The stripped gears explain why, at the time of death, the mixer was running but the beaters weren't turning; I therefore feel confident saying that these were the cause of death.
Plastic gears that go bad quickly are a big complaint among the hardcore mixer-types; however, certain plastics can be really strong and durable, even compared with some metals, so I don't think plastic gears always necessarily equal shortened mixer life. These gears were likely designed to last only a certain number of years, and my guess is that they met or exceeded their planned lifespan; therefore I am ruling, in this case, that the gears were stripped over time due to natural causes (friction, etc).
You'll notice the name "Chefmate" on the far left side. If you ever come across it, keep my story in mind. The thought that I might make a difference in even one person's baking experiences makes it all worthwhile.
Rest in peace, little Chefmate; rest in peace...