I was actually just making the joke that my mum wasn't in fact fat (because she is see so it's like irony but not however she's actually not and I just made it all up for the joke). Largely I'd hold that the actual confusion in this issue arises from linguistic differences, ie we don't actually define what we mean by "know". This happens a lot though so it's not really too big a deal. After all an empty box is rarely empty!
Edit: Apologies horn, I never actually told you what I was reading, A Contemporary Review of the Theory of Knowledge or something like that (i can't see the book right now, hidden among the other, forest, trees, double zing, etc). Anyways it was by Robert Audi. I didn't like it that much, bit of a tome really