If your BitTorrent client downloads suddenly became slower, although you have not posed any limit (you left “0”, which is the default, unlimited, speed for downloads), see if you have changed two other settings that effect performance.

Go to “Options” > “Preferences” > “Bandwidth” and make sure “Apply rate limit to transport overhead” option stays blank (without a check-mark).

Now BitTorrent should again take advantage of all the bandwidth your internet provider gives you. “Apply rate limit to uTP connections” should be checked though, if you want to define download limits. “Stop transfers on user interaction” should be unchecked.

Enjoy!