Everything and anything can become subject when "lightening damage" is concerned. I suggest you pull AC plug at the psu next time(5min.), replug when ready for use, it should reboot again. Of course, it can be your HD as well. Otherwise, I normally suspect the mtrbd. is getting flaky and/or the start ckt. is kaput, no fix, but replace. Don't take anything for granted, test elsewhere and rebuild system.
Here's the story. Recently my computer (home built with asus mobo and ultra 400w power supply)was hit by lightning and thus it would no longer powerup no mobo lights. I bought a new power supply ultra 500w to replace it. I put it in the computer and it powered up fine, and I ran it normaly for hours until I went to bed. I turned off the computer and the next time I tryed to use it no mobo lights and no power up. I replace the power supply with an identical from the manufacturer. I plugged it in and again it ran fine until I left the computer off for some time. I guess the mother board is feeding back and burning up the power supply only when the computer is powered off. I would like to know if my guess is sound, but I have never heard of this so alternate theories or suggestions of repair are needed.