We are tomorrow going to give varied advice about deleting the LW preferences folder. This is because from LW 4.16 & earlier the download preferences were stored in the incomplete folder, whereas in LW 4.18 & LW 5 the download preferences are stored in the main LW preferences folder. Thus that's always the risk that LW 5 will not recognise the older incomplete files.
There is a file within the preferences folder called
Downloads.dat which stores the history of the incomplete files.
At present, LW 5 is a little too basic to recognise old downloads by itself. It also has no resume function unlike LW 4 has.
My advice would be to re-search the same topic files, hoping that upon finding sources/hosts ... LW 5 will recognise the files.