Try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #3 in Fixes for Limewire (sample image included at near of page.) Make sure you remove the Downloads.dat file from this folder first before you do this!
After deleting the preferences folder, open LW only for a moment. Then close. Then re-add the Downloads.dat file to the new preferences folder.

Be careful in each step of doing this ! .. Make sure LW is not open .. and make sure you remove the Downloads.dat file before deleting the preferences folder. And only return the Downloads.dat file after you have closed LW after a short opening. This will retain your download history. Note: The Downloads.dat file might only be called Downloads in your preferences folder if extensions are hidden.

Perhaps, just in case of a mishap in the process, make a copy of the Downloads.dat file from your LW preferences folder. In that way you can always go back to that copy (save the copy to a different hard disk drive partition such as Drive E would be ideal!)