Aaarrrgghhhhhh !
I see this with our company sometimes too. I am not in sales, I am in billing, so I get to see/hear when one of our sales folks lands a very lucrative company, only to have our IT not get the interface between us and them right, causing major billing errors, which doesn't make new companies happy at all. Sure we straighten them out.... eventually and hopefully before they go back to who they were with before, but what is worse on our part is that we have done interfaces a LONG time and there are not many office software programs that our clients use that we don't already have interfaces with in with other clients offices, so setting up a new one should be a cake walk.... but is it ?... Ugh... not always, which means headaches all around.
I have faith that with time you will figure out a new strategy to still land this company. I can see how that delicious looking breakfast helped.