I have heard of your problem before, and personally ran across it once in the time i have been turning wrenches, professionally working on cars.
Let me ask you this.
What type of upper ball joint do you have in your upper control arms?
Believe it or not, there are different "styles" of ball joints between the manufactures.
If you have a ball joint thats "tall" in it's design, it can have the grease fitting rub on the inner diameter of the wheel.
I have enclosed a picture of two upper control arms, side by side.
One has a "normal" ball joint installed, and the other has a "taller" one.
Hope you can see the differences in the picture.
Might help you out with your problem. Good luck.