Hi Eric, welcome to the FileMaker comunity!
This problem does not appear to be a bug of FileMaker Pro. A better place to ask this question would be the FM Pro Forum.
I am not sure if I understand your problem right. But I will give you some information that might help you with your problem.
The reason why Inspector options are grayed out, could be the selected object is part of a group (multiple objects are combined as a group). You can ungroup objects in the Inspector (Position > Arrange & Align > Group > 2nd button).
FileMaker Pro 12 uses Layout Themes. To copy Themes attribute (its style) use the appripriate buttons in the Inspector: Appearance > Style > 1st/2nd button.
If you look for a way to change the round corners, you can do that in the Inspector as well: Appearance > Graphic > 4 Buttons behind Corner radius.
Regards, Arnold Kegebein