RAM would have been my first guess, and I'm glad you know enough to check that first as well
Power surges can cause this, but you would likely notice a smell of burnt colou
r somewhere around the power supply.
If power is getting to your standby lights, then it's hopefully a good sign... most likely your motherboard is fine, i've seen them go on many models and i most cases you get nothing... absolutly nothing happens.
Although your computer is plugged in, that little battery can still run the show, it is the starter motor if you will of you computer, keeping track of more than jsut the time when you turn you computer off.