I had about 100 prefabs with labels that were all TTF fonts. I dropped them all in, in the filter box i typed in UILabel. Then with them all selected I clicked on the font type box and changed it to NGUI.
Then I applied all the prefabs.
How I noticed this problem in the first place is that the default font size # was showing 25 which was the UILabel.fontSize variable value instead of 64 which was the NGUI font file size.
Thats when i put a breakpoint in the UILabelInspector class and saw that the default font size getter was determining that the ttf font was not null and returning the font size itself.