I don't know if you can really get sudden cases of backlight bleed, especially in two areas. Is it maybe possible that it's always been there and you've just noticed it?
Have you maybe changed the settings, or has the set had an update which has changed the settings?
The set that I have only shows the problem on certain things; I didn't notice it for a while. It's never visible when watching normal content but when I put iPlayer on it's visible on the plain grey background. Also, if I change the picture mode this can accentuate it.