Also after you've completed dwnlding a file (there might be) remants left over in the incomplete folder. LW is not perfect; sometimes it starts a dwnld from one source/grp of sources & another time it forgets about it & starts dwnlding from a different source creating a new dwnld file. I believe it has something to do with the hashing of the files (highly possible a Java issue since java apparently has some hashing probs - I think I'm right about that from what I read just recently.) I've has the experience of having 'several' copies of incomplete files left over in the incomplete folder despite finishing the dwnld - or even not yet finishing it. (Search for thread called 'library items in red' on this forum. It gives an explanation why.)
This might not be your issue but it's just another possibility.