when you do your searches next to the quality there is this #.
under # there may be a number. The higher the number the better chance of a successful d/l. This number represents how many hosts are sharing the file.

It also depends on the host u/l speed. If your on broadband and they are dialup. The host has a slower u/l speed than your d/l speed.

If there are few hosts sharing this file, and they disconnect. You will lose your sources for the d/l, and will have to wait until they connect again or LW to find another source before the d/l can continue.

Hope this helps