Maybe the file that you're trying to rename is in use because you're uploading it (ie someone else is downloading it from you). In LW's library, right click on the file > stop sharing file. Now the file name will show in red text.

Highlight the file in LW's library > click on Explore. When your saved folder opens outside of LW, try renaming from within the saved folder, rather than from within LW's library. Keep your saved folder open & shut down LW... see whether that's any better.

To start sharing the file again, just right click on it within LW's library > share file.