"do you want to quit the game" message pops up constantly

I have a white darth vader psp and was playing GTA vice city stories and every few minutes i would notice the message "do you want to quit the game" comes up even though i don't press home. I also noticed it will happen if i lightly tap the psp UMD door it will happen but it doesnt do that for any other games. i've played clank, MGS, ATV offroad, and socom but they are fine no matter how hard i tap the UMD door. I don't know if its GTA VCS because it works fine on my brothers silver daxter psp.

Yeah... mine's been doing that too recently. But quit doing it after a while.... I think maybe the case got warped or something and the start button is bunching up with the case pushing itself in or something.... Anyway doesn't happen as often, anymore. I don't have the Darth Vader one... I have the Daxter one, but it's a 2000 model, like yours. I squeezed it pretty hard the last time it did it out of frustration.... and it stopped randomly doing it thus far. Guess I squeezed it in the right place. For me it was doing it on all my games...

Not that I have a lot... FFVII:CC, MHF2, Hotshot Golf, Star Ocean, Yggdra Union.... Those are about all I've been playing recently.

repairs... how much does it cost? i have no warranty. im not gonna get it repaired now since its fine with almost all my games. but when it turns to **** then ill consider it.