Freezing psp

For some reason my psp freezes if you press two D-pad buttons at the same time. What happens is the screen freezes and then it shuts of after about 10 seconds. This also happens sometimes using the internet browser. Also, the problem seems to be getting worse because the usb isn't working right anymore. I don't know what the problem is, maybe a key is messed up. I think the problem started around when I upgraded to 3.40 OE-A, but that might not be the cause. If anyone has an idea about what could be wrong I would appreciate it, thanks.