Which version of LW & Java are you using? Make sure you have at least Java 1.5

Go to your LW Library window, select the Incomplete folder & arrange it alphabetically by clicking on the top of the column. Then see if you have more than one listing of the same file. If no then see below.

Make a note of all your settings & then delete your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.)