BB Curve :: 8900 Displays Plain White Screen?

I've had my 8900 for two years. I really love the phone, but around the beginning of December 2010, it started doing something funky. It seems that when I am either talking on the phone for a long period of time (around 15 minutes or so) or in the middle of a movie or while taking a video, the phone will go to a plain white screen, and it is impossible to turn it off or have any other interaction. In short, it freezes on that white screen. At other times, it will power itself off, and it also appears frozen, with no possible interaction. In either case, when I remove the battery for a few minutes and replace it, sometimes it comes back on, and other times I have to plug it into a charger, whether it's a USB cable or AC charger. In any case, I may have started with a full battery, but after this, the battery now only shows three and a half of five battery blocks. This is not limited to the OS, since it happened with the original OS back in December (4.6) and continues to occur now that I have upgraded to OS 5. It seems to be hardware related.