Usually, when I have right clicked on a file or folder, clicked on "properties," and gone to the "sharing" tab, I have seen both the option to share between members on the same computer and members on a network. Last night I realized that I totally lost the option to share with other users on my computer; no radio buttons, no option at all. It doesn't even show up on the properties windows. What happened?! I have no idea what to do.

Please help.