incrediBILL - 7:00 am on Jul 14, 2010 (gmt 0)
it always seems like theres that small percentage who are just dense
They're having a technical problem, such as the cookie failing or something else.
I've seen all sorts of nutty things happen that shouldn't, inexplicable, usually about that 3% you seem to have issues with as well.
The best anyone can do is streamline it until it's completely idiot proofed and after that it's anyone's guess why it still fails (if it fails) but at least human error has been factored out.