For all you PSP slim experts out there, could I get some help?

Here’s the thing. I have a PSP slim (modded), and it’s running 5.00 m33–6. I haven’t played it for a while, and I also haven’t done any firmware and kernel updates since Final Fantasy Dissidia came out. So recently I downloaded Disgaea 2 and Gran Turismo, and when I select either one of them to start-up the game…the screen turns black. I would then have to pull out the battery; put the battery back in; and turn on the PSP again as all keys including the on/off switch become unresponsive. I have a feeling it has something do with the firmware and kernel, but I don’t want to start installing random things on my PSP, as I’m afraid I’m gona “brick” it. Is anyone knowledgeable enough to tell me what I could do?