Try forwarding a port using your router's instructions (or enabling port triggering, whichever you choose). Then start a bittorrent download on the port range you have set to forward to your machine. While it is in progress, visit
http://www.grc.com. Click "Shields up!" then scroll down to the "Hot Spots" section and click "ShieldsUp!" After reading their disclaimer, click "Proceed." In the text box, type the port range you have forwarded for bittorrent. So if your port range is 6881 to 6889, type:
6881-6889
in the text box then click "User specified custom port probe."
If you did this with your ports properly forwarded it should have no problems connecting to your bittorrent port(s) while it is in progress. If grc.com is having no problems connecting to your bittorrent ports yet all the torrents you try to download are always yellow no matter how many peers there are on the torrent, it may possibly mean your ISP uses a transparent web proxy that proxies your bittorrent tracker connections which causes trackers to not be able to see your computer's real IP address and therefore causes other peers to not be able to connect to you as a result of not knowing your real IP address.
http://www.all-nettools.com/pr.htm might be able to tell you if you are behind a transparent web proxy or not.