Chinese short stay visa for 10 hr short port call on cruise ship in Shanghai?

I am an Australian citizen ....went on a cruise last September(2012) and because I used my single entry visa on business in Guangzhou before getting on the cruise ship in Hong Kong I was not allowed off the ship when it stopped for 10 hours in Shanghai!!! Was this correct...did I need a second entry for Shanghai. I am under the impression that Shanghai waived requirements in 2000 for short stay visits. Please advise if I did need a one for that stop over if anyone knows!