ALSO - If they are Facebook/Twitter sweeps, you have to be a PLUS member to save them.
Facebook & Twitter Contests will not save because they only have a place to be saved in PLUS - you either save them to that category in the drop-down, or into whichever category YOU name.
So while you may see those listings, you may only add them to YOUR My Sweepstakes {in the Facebook/Twitter or your own category} if you have PLUS.