I can sympatize with you, because I almost didn't get my student visa when I returned to SA after aupairing for a year..
Many of my friends that have returned to SA after being in the States have been really unhappy and are also looking for avenues to return.
If you're interested in redoing the au pair option I would look into these web-sites, where au pairs and families can hook up without an agency (some may require an agency after the match) But it allows you to have contact with numerous families before deciding. Also because you couldn't get a J1 again, look into your other possibilities (H2, or the 1 year extension on your J1 - I'm not 100% sure but look at the (visa) website : http://www.immigration.gov/graphics/index.htm)
Au pair websites (a friend of mine in Gurnsey used greataupair.com, the family she matched with flew her over on a tourist visa)
Some of my friends have also worked at a Golf Course on Long Island, this option is only avalible in the summer though, so if you wanted to wait a year, you could look into that. I'm not sure what the south african connection is, but if you're interested, I could find out. You can have a look at this site in the meantime
Also work on finding solid evidence that you plan on returning to SA - a letter from a company is in my opinion the best, even a spouse - heck! "get engaged"
If you have any questions, please e-mail me at Charlenecpt[at]aol.com