Never heard of this before. The Crack sound and a Freeze situation. When it fails to boot what exactly does it do or not? Have you tried on ext. monitor when it fails to boot? I'd start here.. If its the Screen backlight its possible the sound you heard was approximatley 1.6KV ac snapping to ground. This could definitley cause a freeze state due to the discharge. You may have a slightly chaffed or loose inverter cable, and this coupled with high humidity might have arc'd the voltage outside of the CCFL.. (I'm just guessing at this point).. We'd love to diagnose this one for you if you'd like.. Good luck!
Ken
www.ikenfixit.com