Visa cancelled at Pudong on arrival!

Hi there, I recently was given a business visa through a company in China, Which I used perfectly well in February this year to travel to China, while I was there on this visit I became ill and had to come home, on Wednesday this week I flew back to China as I had recovered.
On arrival in Shanghai I was advised my visa was cancelled and had to leave China there and then.... I was given a return flight to the USA, and it was stamped as "cancelled", there was no warning of this, and so I had basically thrown $1400 down the drain, the money is nothing compared to my fiancée waiting for me in Nanjing!
It was suggested that the company that gave me the "invitation letter" had cancelled my visa..... I really need to know my current situation where it is concerned. It now sports little blue cancelled stamps; will this prevent me getting a tourist L?
By the by the authorities at Pudong were very friendly but gave no clue as to why this had happened!
Thank you in anticipation of a positive reply!