MBP mid-2009 boots to Gray Screen, keyboard commands unresponsive

I have a mid-2009 15" MBP that will not progress past the gray screen at startup. When I press the power button I hear a normal chime, then nothing. No apple, no progress bar. The hard drive is an SSD I installed a couple years ago, so there's no spinning to listen for.

I have tried every keyboard combination I could find on the internet, but still nothing (recovery, single user, safe, etc).

I was able to reset the PRAM (got a double boot/chime) and the SMC controller. No effect.

I plugged in a bootable USB drive, dug up old install disks, and tried an external keyboard as well. Nothing! On startup the CapsLock button lights momentarily on the external keyboard then goes out. Pressing it afterward does nothing.

I can hear the CD/DVD spinning but it won't mount or eject.

I do have a genius bar appointment later this week, but is there anything else I can try before I take it in? I'm assuming it's some kind of hardware issue, but I don't know where to start.

Thanks for any advice!!