I'm guessing that you don't have scope or logic analyzer to actually see whats going on, I think thats the only way you're going to fix this. In this case I suspect a scope would be more helpful (USB from eBay £50 ish - for this you don't need lots of bandwidth) and as they are so cheap, Salea knock off (eBay £6). And before the winers start, a) Salea don't sell them any more and b) if you base your software on a reference design you shouldn't be surprised if people use alternate hardware.

George