Hi, I've had the same problems for about a month now. I have a psp fat (psp-1000) with cfw. 5.50. I was playing ZHP unlosing ranger when the same thing happened.
I use the lowest brightness setting to lengthen game play time.
I keep using the audio button (The one you hold and turns the sounds mute or back.. right?) for the game then when i reset my game (press home and start the gameover..) the brightness suddenly keeps on changing even making the whole screen black. After 5 minutes? it stops but then when i press the down or square, triangle button the brightness changes sometimes thats the only thing the button does.. i found a temporary fix for this, i put it sleep mode then turn it on again and it stops.. the buttons go back to normal, for a while.
It goes on and on even with other games. It just stops after 10 minutes later or more than starts happening again everytime the brightness or audio button is pressed.
We scanned it for viruses on a computer and it just kept on blinking everytime it responded to the scan. No virus were found but after that when we disconnected it from the computer the brightness problem stopped for a good long time.. we avoided pressing the brightness and audio buttons. but recently its happening again.
and now just got worse. I was playing Socom Fireteam, and when you accidentaly go to the start menu, you have to press "select" to exit and continue the game. But the "select" button wont work!
so i quit the game and startover..
when this happened for the 3rd time. When i pressed "home" button and was asked if i really wanted to exit the game i couldnt move to "yes" and couldnt press the "O" or "X" buttons.
So i turned off my psp and when it went back on, I couldnt press anything anymore. except, the volume buttons and select (the vsh menu appears)
I searched for help from the internet, found "disable your vsh menu" remedy.
It worked! but when i played the game, the "cwcheat" menu keeps on appearing (seplugin that appears when you press select button). It wouldnt stop >.<
So we disabled that too.
Now playing God of War Ghost of Sparta, and one part, the start menu kept on appearing! we'd close it so that we could push one of the levers in the game but then it pauses the game again.. it stopped after a while. then it happened again only slight.
Found a comment on a "select button problem" and it said that it was the:
"parts that were Ribbon style, with it was the start and select button and the volume/sound" he had that parts?
found same problems around the net, some posts from 2009.
found decent posts and solutions here:
the best one says buy a new "flex bar" or "home bar". It goes by many names, but it's the metal bar that has all of the bottom row buttons on it (home -> start) It's usually under $10 USD and obviously the right thing to do.
got another comment that says it worked from him when he bought one himself.
Glad I found others, and that I could share this.. wish it makes things better.
Hope it works out for all of us!
Another thing, Merry Christmas!