
This was a new SKF bearing a year or so ago, we removed the half-shaft for something else and part of the outer race fell off !
It looks like it's been cracked for a while and removing the half-shaft caused the last few mm to let go (the last 3-4mm was clean and grey, the
rest was dirty/oily).
Have I done this whilst fitting ? I can't remember having any problems or seeing anything untoward, but I can be a bit heavy-handed at times
I'm not shelling out top money for another SKF, McGill motorsports on eBay are selling them for a tenner delivered, that's where my
money's going 
bad luck, at least you caught it before your shoes got soaked in gearbox oil!
Edited to add...
The side thats broke doesn't really take any stress during fitting so id put my money on just part failure during use...
[Edited on 26/4/10 by prawnabie]