I used to use ABC faithfully, but uTorrent is worlds better. I'm a convert.
Anyways, Que, your internet is going slow because your upload speeds are probably close to the cap set by your ISP. Download barely affects internet speeds, but if you're on cable and your uploads are going over, say, 35 k/sec (maybe lower, maybe higher depending on your ISP) then the rest of your internet will crawl. I have comcast, the upload cap seems to be around 55 k/sec, because I've never seen it go higher than that, and my internet is practically useless at that speed.
So, check your torrents, see which ones are uploading and right click > properties on them. Change maximum upload rate to something small like 5. You'll still upload, but your internet won't take nearly the same hit in speed. Know that sometimes torrents go slower when you upload less, though, so if you want something fast, set upload to unlimited, or 15 or something.