This might be bumping but...
Well I had the same problem, I am in the UK.
It seemed to me that my ISP was throttling me because of my overusage of the internets. I use bittorent an awful lot, and when I stopped using it as much my NAT was always open, and I could join anyone.
It also seemed that it was only people on the same ISP I can join, maybe the people near you. I use BT.
When downloading stuff, my advice is to use a VPN like
http://www.relakks.com, that way I don't /think/ ISP's can detect how much you're downloading.
Meh, it worked for me anyway, after using a VPN for downloading I was no longer throttled.