hi tegboarder
here's how on OSX. Find and select the shared folder on the hard drive (not through the Library Pane), and use Finder->File->Get Info. Look at 'Ownership & Permissions' and set the boxes the same as a newly created folder on the desktop. You can find out more with the key words "access + privileges" in the OSX Help.

If the permissions are already the same (probably), then in LimeWire, use the Preferences->Sharing->Add button to add the folder you want back to the list of Shared folders.

You can also look for more ideas in the LW Help->Tip of the Day. For example "Frequently see 'Could Not Move To Library' on downloads? You can fix this by making sure a valid save directory exists in LimeWire -> Preferences, Saving and reducing the amount of files you're trying to download at one time."