I've had my 60D for about 6 months now and it's given me remarkable service. Until the last couple weeks. 
Today, for the second time, I've picked the camera up, attempted to turn it on and found the battery completely drained. Dead as a mackerel. No beeps, whirs, clicks...nada! Both times the camera had probably 60% battery left, was unused maybe 5 or 6 days and then there's not enough juice left to power it up. Previously, with light usage, I've gone weeks at a time between battery recharging.
Any suggestions of how to possibly determine if it's something wonky with the camera or maybe just a flakey battery? It's the original battery shipped new with the camera. The camera's never been dropped, bumped or booted around or even exposed to rain. I don't think I've even had the lens off it more than 3 or 4 times since I've only got the kit lens for it so far.
The battery is on the charger presently and I'll put it back in tomorrow morning and see if it still acts up again in a day or two.