Macbook Pro (early 2007) screen backlight problem (fixes temporarily with smc reset)

Hi all. Maybe someone can help.

My Macbook Pro was one of the units afflicted with the videochip/logic board thermal paste issue and Apple replaced the logic board a year ago.

I am having an issue that I can't figure out (I had the same exact issue a few months ago and it resolved after several smc resets)....

My screen backlight will flicker and then go out completely about 3 minutes after booting up. The ONLY way to get the light back on is to remove the battery, do an SMC reset and then it will work again perfectly....for about 3 minutes.....

The display is there....just not backlit... Also, once or twice the computer booted itself into safe mode (I presume, because it said there was no wireless hardware)

I have tried SMC resets, pram resets, shutting down, going into and out of sleep, etc....

Has anyone else seen this problem?

I am confused by someone I know saying it could either be the inverter or inverter cable or the logic board. I say this because the computer will reset itself (albeit for only 3 minutes each time) and the backlight will work perfectly (again for only 3 minutes) after an smc reset....every single time.

Any ideas?

p.s.....when this happened before and again this time, the computer was in extended sleep mode in my travel bag.....

Thanks for any answers and please let me know if you need more info......