Hardware Random Black Screens

[Romsstar]

I got a new battery for my PSP 1004.
It seems third party, no SONY logo, 3600 V.

I have CFW 5.50 Prome-4 on my PSP.

The thing is since then I have occassionally random black screens with the green light turned on.
I had it first at a scene in a game and then when I tried to copy sth via USB to the PSP.
When such a black screen happens I can't even get my PSP turned back on.
I have to put out the battery but when I put it back in it won't work.

But when I connect the PSP through the AC adaptor the battery keeps charging and everything seems fine again and I even can turn it back on.

Also: I couldn't copy the file with the battery in but with the adaptor (battery out) everything worked just fine.
What could be the cause of it?

Also: I opened it the other day to clean it but nothing serious happened and it seemed all fine after that.
Still have this problems since yesterday. Any help?

 

[Rydian]

Do you happen to be pressing the L or R trigger when it happens?

 

[Romsstar]

No, this would put it in Recovey Mode after all, right?
But this happens after a short time and apparently for no reason.

 

[Rydian]

It'll only boot into recovery mode if your memory stick has been formatted to be a magic memory stick and has the right files to boot on it, otherwise it'll just give a black screen.

Dunno' what it is then.