MBP won't start if it cools off.

My late 2008 MBP has developed a seriously weird problem. If I shut it off and let it cool down, it won't start again. (To keep it operational I can put it to sleep - but I can't shut it off.) I took it to the Genius bar and they said they didn't see anything wrong with it and I should buy a newer unit.

That's unacceptable.

So here's what I've done so far. I researched startup programs theough Apple Support and this user community as well as some general web sites. I've done everything up to and including resetting the SMC. If the laptop is cold, it still won't start.

However - I found that warming the unit up to an ambient temperature of about 80 degrees and resetting the SMC will allow it to start normally. Once I have it running I can keep it running just fine by not turning it off. I can let it go to sleep and it wakes back up just fine - I just can't turn it off.

I'm about at the point where I've decided it must be a solder fracture issue. Somewhere there's a connection with a hairline crack that contracts just enough when cold to break contact.

Anyone else have any ideas?