Updating should cause absolutely no problem at all!!! But if you update & then change back to opening an older version, then LW may refuse to load the incomplete files depending upon how far back the version is in development.

If they refuse to initially load LW 4.12.+ will be able to continue files from last point in downloading. Go to the LW Library window, select the incomplete folder, hold SHIFT key as you select the 1st to last file in the incomplete folder & then press the Resume button. This will force them back into the download window. For only LW 4.12.+ they will resume from where they were.

BTW other reasons why you might be having your problem: Downlds refuse to reload (click on link)