There can be a number of reasons.

1. Limewire is extremely slow and inefficient - try xNap and Poisoned if you are on OSX, they work much better for MP3s

2. You are dependent on the other person(s) in the peer to peer connection to keep sharing and to not change the name of the files you were downloading. People are unfortunately not good at being cooperative. It helps if you keep your connection up and sharing continuously and for as long as possible to give others a chance to comp-lete their downloads. Files tend to have dumb and sometimes wrong names so people change the name. As far as LimeWire is concerned the file has now disappeared and there is a new file to download.

3. Are you sharing as many files as possible? If you are not, then the peer's LimeWire freeloader settings may be set to filter you out.

4. Check your connection quality. Down the bottom left corner is a mini bar graph showing how well the connection is going. It fluctuates constantly.

5. I find LimeWire to be extremely stupid. It needs to be nudged all the time to renew downloads. Right mouse click on the search bar tab and keep re-searching your parameter.

To sum up: Poisoned particularly gives a much faster and reliable download. XNap takes a bit more setting up but also spans several different nets and hits many more target peers.

A simple suggestion for you is to post in the General Forums if you wish to introduce/push a client which does not currently have a specific forum here.