My PSP's home/volume buttons don't work?

Hi, recently my PSP’s home button and volume buttons have stopped working, the volume is stuck on full blast, and my home button no longer does anything, but the strange thing is, the display (brightness) button works as a home button.
My PSP is about 3–4 years old, and this is the only problem I have ever had with it. I am running 5.50 Gen d-3, and when I open the VSH menu, I cannot exit, as it will freeze my PSP’s XMB.
I have already downgraded to 5.00 m33–6 w/hell cats recovery flahser, The VSH menu still froze :(. I have also tried disabling VSH menu, that did nothing, and using the hold button did nothing.
Chilly Willy’s key cleaner says I have O.K. keys.
I have opened my PSP up, and there seems to be no dust etc. on the buttons/connection ribbon cable.
I have formatted flash0 and nothing changed.
I cannot buy a new PCB bar on E-bay as I do not have a credit card/paypal.

I have not dropped my PSP or submersed it in water!!!
Any suggestions, please? I am very confused and was about to upgrade from a 1 gig memory stick to a 16 gig memory stick… also please do not answer with: “Go get it repaired by a pro or send it to the company.”

OK, TO CLARIFY THE WARRANTY W/ SONY IS GONE AFTER ONE YEAR, SO OPENING MY PSP UP WOULD NOT CHANGE MUCH.