Perhaps you have collected a few too many incomplete files along the way. Tip: Purge the Downloads Queue! (click on blue link) can help freshen LW up.
Remember there needs to be hosts for the files online for the files to continue downloading & they also need to have upload slots available.

yup they have people sharing etc.. because if i cancel them, then search for same file again and start downloaing, it runs like the wind!!! its so annoying!!!! nothing is helping my poor downloading..