Try downlding a magnet link from here & tell us what speeds you get & how it behaves: http://www.magnetmix.com/video.shtml

Might I suggest you go to LW's menu bar, Tools>Options>Speed & disable Ultrapeer capabilities. Also iTunes>Sharing & disable sharing option. Press Apply button after all changes.

Can you also tell us which ISP (net provider) you're going thru to get connected to the net.