Faulty, old phat PSP...need help!

Okay my PSP has a long history, and it's being making me go crazy now because I can't figure out what's wrong with it.

I bought my PSP back when it was just out and it had official firmware 1.00 on it. Later on I upgraded it to official firmware 2.00, but downgraded it using the TIFF exploit back then to 1.50.

Later on, I upgraded my PSP to fw 2.60 because I wanted to play a game really badly (forgot which) and later I downgraded it using the initial 2.60 GTA:LCS exploit.

Later I upgraded it to 3.03, but once again downgraded using the 3.03 GTA:LCS exploit, then installed 3.03 OE-C, and then to 3.40 OE-something.

It was somewhere during 3.03 OE-C and 3.40 OE when the problems started--sometimes my psp would be able to identify the memory stick but I wouldn't be able to access it (as in if I press O under Music, the loading circle at the bottom right corner would turn up for one second, and then nothing would happen), or I wouldn't be able to access my saves in games although a few minutes ago I would be able to.

And then very often I wouldn't be able to turn on my psp, not even to recovery mode; when I power it on the green light would come on, but the screen remains black and after a while it turns off again.

Also, as I play both Japanese and English games, sometimes some of the Japanese characters would turn up glitchy or missing during a game.

Sometimes it would work fine for hours on end only to crash unexpectedly.

Then afterwards the problems got even more serious and I started to get red screens of deaths all the time. I got scared and downgraded and upgraded it back to 3.40 OE to no avail; the problems were still there. I tried formatting flash1 in recovery menu but it didn't help either.

Finally when I tried to fix the Japanese character problem by changing the language setting, it landed me with a blue screen of death where I pressed O and then my PSP was officially bricked--every time I powered it on only the green light would come on.

That was all one year ago, but then a friend of mine offered to help me fix it, and he did! My PSP came back as a functioning, 3.90 M33-3 PSP, and boy was I excited. I rummaged through my drawer and started playing Monster Hunter Portable 2nd again.

And then I started noticing the Japanese characters were turning glitchy and disappearing once again; and there were two times when I went to save the game, the game would be stuck at the part right before it saves (not a hang though, because the game is still animated and stuff) and when I try to exit via Home the PSP would just switch off.

And then today, when that happened, it wouldn't turn on or go to recovery mode until I plugged it into the A/C adapter and another time it couldn't read the memory stick; and then at one point I got the red screen of death when opening the game.

So all the old problems are returning! Can someone please help me figure out what's wrong? It shouldn't be a firmware related issue as I had re-installed 3.40 OE and now my friend flashed 3.90 M33-3 using pandora's battery for me, and yet the problems are still here. Could it be related to idstorage key problems from my earlier downgrades?

Don't know if any of you are going to spend time reading this...but I'd appreciate any sort of help!

update// I just did a quick run with the idstorage KeyCleaner 1.4 and all my keys were fine, except for the 0x46 and 0x47 which are missing from all TA-079 machines anyway. So it seems like idstorage keys arent the problem...What can it be?