hey yuki,
well, the first piece of advice would be "don't squeeze it"
not sure exactly where you mean, but the case on my G3 500 mhz Pismo certainly doesnt allow for an external squeeze to affect internal components. is yours damaged or cracked?
do you have a fresh battery installed? the battery would be my first suspect, try a known good one.
do you have any screen symptoms--the area you are talking about (i think) is where all the screen wiring travels, so if the case is broken, i could imagine it impinging on wiring.
and if you have nothing else to do (and better than squeezing your PB case), reset the power manager, zap the pram and make sure your power adapter is working and charging your battery.
best wishes,
rich (pismo g3 500)