Hi whizbang,

What you saw was LimeWire's "partial file sharing" (PFS). PFS allows LimeWire to immediately share back files you are downloading. If you view the 'Incomplete' folder in the library, incomplete files that are eligable for PFS are listed in black. Files that aren't eligable are listed in red (much the same way normal files in the library are listed in red before they are shared).

If you don't want LimeWire to share partially downloaded files, you can uncheck this option in your Options. I believe the choice is part of the upload options.