There are fake files around which will sit connecting for ages & then go straight to 'need more sources'. For these ones, search again & stay away from files with a huge number of sources (go for a file with 10 sources or less & also ones with a modem source).

For the slow speed, try deleting LW's preferences folder when LW's closed. See points 2 & 3 below
Fixes for LimeWire

What are your details?

OS(Win XP etc)
LW & Java version (help > about LW & you'll see)
Firewall you're using
Modem/router brand & model
ISP
Connection type (DSL etc)
Where you connect from (home, school, student accommodation etc)
Are you sharing a connection with other computers
Is this your first try with LW
Have you tried other p2p apps & if so, do you have the same problem
Do you see the firewall icon (brick wall in front of the blue globe)?