When you have a program like a torrent client throttled to upload at the maximum. Your other programs aren't going to be able to communicate with the net very easily (if at all). I have road runner and I get upload like 40kb/s total. Inside most torrent clients, you can throttle the maximum upload. I changed mine to 10kb/s. My download speeds jumped higher on my torrents and my other softwares (internet explorer, aim, yahoo, etc) they all worked like I wasn't downloading anything at all.

If you want your share ratio to improve on a torrent site, re-up the maximum upload rate and walk away. When you come back, Internet explorer, etc will not find the 'net easy. Lower the max upload again and bam, it all works just fine and your torrent download speeds increase. It's amazing!

BTW, lowering your upload rate will NOT affect your download speeds.