I open the case to solve grey startup screen - what could it be?

Question

Lately I've attempted to wake my powerbook after moving between home and work (generally by bike) and get no response. Cold reboot and subsequent attempts at startup result in a chime and grey screen with no apple. Booting from startup disk and looking at disk utility shows a HD with no volumes that appears unformatted. Resetting PMU, PRAM, NVRAM doesn't help, however if I open the case (i.e. take off the keyboard), tweak the various cables, tighten any loose screws, blow off the dust for good luck, etc., then put it back together, the machine works like there were never any problems....for anywhere from a day to a week, when the same problems happen again.
To be fair, I give the machine a good workout and have for the past 3.5 years; daily half-hour bike rides in my laptop backpack (mostly smooth, but some bumps), every workday spent docked to my work keyboard and monitor, thus running with the case closed and an occasional paper or light folder on top of it, and about 3 years ago it took a spill and as such has a dent on the lower right where daylight can peek in. But the HD seems fine (when it's mounted) and all the various slots and ports and cards seem to work (again, when the system is actually working).
Any idea what this could be, or even how to test? Could an errant wire misplaced cause a short, or some small bit of dust be getting in the way? What problem would be fixed by unscrewing and opening up, then closing it all back up without doing much of anything, and yet be brought back by a transport home?
thanks for any advice or test recommendations. My current plan is to take my friend's old powerbook with a busted display, and swap in my display and HD, on the assumption that my logic board is somehow wonky.

Answer 1

Well, yes, that's logical and all, and probably right, but as a poor grad student I'm interested in wishful thinking and squeezing every last inch of functionality out of the machine while I can before I plunk down 2 months (or so) pay, folly though it may be. I can't bear to throw technology away unless it's truly dead.
Is there any component that you (or anyone out there reading this) guess might be likely to short?
And speaking of shorts, on the lower left corner of the powerbook (i.e. the corner closest to the "z" key), under the hood, near where the dent is as it turns out, is a wire covered in black insulation that appears to be connected to a little card nestled in against the lower wall of the case (the wall parallel with and closest to the space bar). The wire runs about 1/3 of the way up the left side, then abruptly stops, and i noticed the very end is not insulated, i.e. I see silver wire. As this is near the bumped part I wonder if it's moving about a bit and can cause a short...I put a piece of scotch tape over the exposed end just in case. Anybody have any idea what this is or if it could be the problem? My guess is a bluetooth antenna or some such. I've never used bluetooth on this machine so I don't know if it's faulty.
Speaking of shorts part 2, one of the times I opened the computer I noticed one of the little metallic spongy pads that run down the right side of the case, near the power button, had come loose and was out of place, so I put it back in place. It seemed pretty uncritical, though maybe I'm wrong?