Also, if you are using Chrome, are you having issue where an unchecked box is not white, but is the same color as the background color? We see this, and the initial reaction that one has is that the box is grayed out when it really is not.
There is a very subtle difference between "Populate Null Values with the Default" checkbox, which is grayed out, and the the other 4 checkboxes that are not. In IE, the grayed out boxes are gray, for us, and the non-grayed out boxes are white - not subtle at all, very clear.
In Chrome, not very clear. Perhaps there is a Chrome setting we need to change? We're just starting to use Chrome, so we have a bit to learn.
So, if you are in Chrome and have same issue that we have, go ahead and check the box - if its grayed out, it won't let you make change; if it is not really grayed out, your click will be recognized:
Here, I've gone ahead and clicked on what appeared to be two grayed out boxes - they really weren't grayed out!
Apparently, there is a Chrome CSS file/element that can be changed to fix this - haven't yet found it, but only starting search, now.