Caller's photo resized on its own!

[hasmuk]

Hi there,
Before, when people called, or when I made calls, the photos I assigned them would take up about 1/3 of the screen. Now their photos:

1) have shrunk to a tiny box in the middle of my screen with a grey background (not nice)
2) have become grainy and unclear

Any ideas of what has caused this and how I can revert to a full size photo?

thanks!
hasmuk