Okay, tested your blend file, and it works fine for me also in 2.76rc2.
Lets try to debug this. Firstly in the exported AC, do you have any lines saying "mat 0"? That's what it would say if it actually was referencing to the DefaultWhite material..
remove the "DefaultWhite" material line and set all "mat #" lines to be -1 of their current value
Doing that is the same as doing nothing. So will make no difference either way, unless your FG importer is bugged.
Also when looking at your picture it would look different if the problem was DefaultWhite, It would not be entirely white, it would be shades of grey.
Okay, I found the problem. It seems in this version of Blender the script will always export this in materials:
emis 1.0000 1.0000 1.0000
Which of course will make it glow white as in your picture. I will look into it, might take a couple of days. Until then, just edit the materials in your exported AC file, and set "emis 0.0 0.0 0.0".