Do you see a brick wall in front of the blue world icon at the bottom of LW's interface? If yes, then you have a firewall issue. See Connection problems? Check here first! (click on link)

Sometimes ... if you're using the Resume/Find Sources function on all your incompletes at one time this can affect LW's connection quality. Therefore it's wisest to only use this function sparingly. Use it on just a few files at a time.