I would return the bike rack. I got one off Ebay for $50 I think for 4 bikes.
I added a hitch extender like this
http://www.prolineracks.com/hitch-extenders.html
You must not overload it - be mindful of your tongue weight. Mine easily carries 2 adult MTB and 2 kids bikes. I have a hitch carrier that I will load a bag or 2 of chicken feed, luggage, etc. Right now it has a 1 7/8" ball and I tow my motorcycle on a small trailer. The bike rack is waaaay expensive. Would return that. I had no problems with the company, but I'd be PISSED if they did that to me.
my bike rack is similar to this one:
http://cgi.ebay.com/4-BIKE-RACK-CARR...item4840fcbb3d