This is just a guess but try to move the incomplete files out of the incomplete folder. Then search for these same downloads in limewire and start the downloads. Then close limewire, replace the new incomplete files with the old ones and restart

Pay very close attention to the filenames when doing this as I am pretty sure that they are noted in the downloads.dat file

And remember this might not work. I have never tried it myself

Please post back if you try it and it works (or if it doesn't ?)