I'm somewhat new here too, but I have never heard of that problem before! Do you think you can give more information about your computer maybe? ^^;
Did restarting the game help, maybe?
As for the grayness / whiteness, as long as you still have your previous maps visible, it doesn't really make a difference, really... unless you're that obsessed (as I was, I must admit) with getting everything white. There are no in-game rewards for getting 100% white-ness.
I think it's also a good idea to point out that areas you are not in will always appear to be gray unless you click on them (I think) to select them, and then your completion appears for those area.