I have just been upgraded to Windows 7. Now my Dropbox folders are no longer sharing, and the option to share with another email address is no longer there?
They changed the way to share with dropbox (using the desktop application). The easiest way I found is to do it via the dropbox site itself. One way to get to it is right clicking the dropbox icon and clicking 'Launch Dropbox Website', log in if you are not already logged in.
After logging in to dropbox and going to the above url, simply click: New Shared Folder and go through the process of sharing. Your folders will appear like normal folders but their contents will be shared.
One can also add new users to a share at the same place, simply select Options of the shared folders and follow the directions.