what does Upload Limit Reached mean?
 

I get loads of people connect to upload stuff and then it says "Upload Limit Reached" and they cut off. Sometimes they haven't even got started.

Anyone tell me why that happens?

In your options you have a "uploads per person" if you have it set too low that will happen. But I might add that if you see someone trying to connect more than a few times and nothing happens it doesn't really matter what number it s set to allow, because He/She just can't connect (often BearShare for some reason)