Sure, I have two separate stories here that might be relevant:
The first company we dealt with was a massive Fortune 50 company early in our existence. They were very interested in our technology, and we were both young and naive. Still, we've been warned so often about dealing with large companies that pretty early into the process we insisted on signing a paid Software Eval agreement. In retrospect, it was a pretty small amount of money (five digits), but at the time it felt like a huge win. From the moment they said "we'd like to try your software", the procurement department was involved -- NDA, software eval docs, etc.
The software eval was "successful" (in fact, we even presented to the CTO, the President, and VP of Engineering of the company), but it wasn't truly an eval. It was a very custom-tailored version of our product for their deployment. And yet it still didn't really go anywhere. Things fizzled out with them for a while and then about 12 months later they came back once again asking to do another evaluation. This time we insisted on success criteria that required them to commit to a set number of seats if the evaluation was successful. The evaluation was successful, and they bought the seats, but even now the deployment is in a state of "proof of concept" -- they bought ~1,000 seats from us, but at their organization size it's just not that material yet. Seriously.
Another company we dealt with was a ~15,000 employee company. They too were very interested in our technology. They emailed us and convinced us to come and do a demo in person. Having liked the demo they told us they wanted to pilot the software. This immediately kicked off the conversation with the procurement department. NDA, software eval, success criteria, etc. This time, we did need to do some additional work, but we were very diligent in making sure that _any_ custom work that we do was applicable to all customers. They too have now bought ~1,000 seats, and are now in the process of rolling AeroFS out to the rest of their company, but as a benchmark, it has been ~12 months since they bought their initial 1,000 seat license. In some ways, even for them the 1,000 seat license was a continuation of their PoC.
Enterprise sales are slow, but the resulting contracts can be quite lucrative. Just make sure you qualify your customers. It sounds like you only lost ~2 weeks on this deal, and that's really not the end of the world :)