My advice would be to

1. Try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included.)

2. Try downlding a magnet link from here & tell us what happens: http://www.magnetmix.com/video.shtml

3. If your files are constantly queued, it may be due to having too many incomplete files & particularly if you use the Resume/Find Sources function on all of them simultaneously which will queue them for much, much longer. Have you considered this: Tip: Purge the Downloads Queue!. Even if you only apply it to those files that are 0 KB / 0%

Are you aware as to which clients you're downlding these videos from? Some users such as Shareaza (Raza) often have many video files but are very slow to downld from & unreliable to reconnect to due to them frequently using multiple networks at the one time. Thus their bandwidth is sacrificed for using it elsewhere not to mention overhead loss due to this multiconnecting. At least one those networks demands they can only downld as fast as they upload. You can right-click the top of the search results columns or downld window to choose to show client so you know which program it is you're downlding from.