Two months in the project lifecycle is a long time for any project. I'm not surprised they gave you the silent treatment. On the other hand, had you asked for more money, I'd be surprised if they balked -- if their offer was genuine.
It's probably something that should be brought up before an offer is made, but I don't think it is a good reason for a company to simply ignore someone they've made an offer to - a polite "no, we need you to start within 2-3 weeks" is an acceptable response.
Edit: The usual spelling update.
Not in the hardware world. 2 months is nothing.