Hi all- late to the thread.
After searching many threads for Macbook Pro Late 2009 Intermittent Crash Battery Startup and everything inbetween, I found the applicable place.
I too have had similar issues. It started in Dec. 2012 with the crashing at startup after the apple but before the spinning grey wheel. Twe weeks later the end of the world came for my harddrive. Total crash, no booting, etc- tried everything, ended up buying a crucial SSD (which I love, btw) and DiskWarrior to recover 90% of files. Long story short, it seemed to fix the problem for a couple days.
Fast forward a week, the crashing begins again, but only when booting on battery power. It would not go to login screen on battery, but after 2-3 tries on AC power, it would finally allow me to login. Once logged in, all was fine, so long as the computer did not sleep. Once in sleep mode, it would not wake and my reboot process began again. When I installed the new HD, I reinstalled OSX, and upgraded to latest version at the time, reset SMC/PRAM/NVRAM, no change. I take it to Genius Bar, they find nothing wrong, say the battery is great, and that I should just leave the thing plugged in all the time... Frustrating, but ok.
By June, the computer crashed so often it was unusable. I was furious and left the computer unused for 2 months.
Now, In August, I just upgraded to Mountain Lion 10.8.4, and it has only done this once, on the restart after install. Plugged her back in, restarted, finished the install. Then I removed extraneous apps (remote access desktop client, spotify, and an alarm clock) from startup, unplugged the computer, and LO and BEHOLD it booted no problem. Repeated the process 6 times with no issues.
Self-EDIT: Hooray for 5 minutes until I spent time to post here and tell you all the great story and recommend updating OSX. Now it's crashing again.
My guess is the nvidia graphics board problem mentioned in other 2009 pro threads. Potentially, software updates until 2012 had kept it at bay, and then the 2012 update unravelled it.
Anyone else actually find a fix yet? I'm visiting the Genius Bar at the end of the week for a final exam and potential logicboard replacement.