Firstly, you have pitched them and they are not interested at present. Remember your startup has a life cycle greater than beta and a peak in traffic for 24-72 hours will not define you.
Be careful what you wish for as you could get hammered. Not all press is good press and a lot can go wrong at beta stage.
Back off for a bit and re pitch again later with a new angle.
Also, split test your press releases and go outside your loop for feedback.
Key things to remember here are as follows:
They may not be interested in your product, period
You are pitching the wrong guys and or going to far up the food chain
They maybe have a pipeline of editorial and it don't fit the theme
Finally
Don't let a Techcrunch post drive you nuts. It's a blog… go dig deep and find real customers. Alternatively, get some people on odesk to systematically go through techcrunch comment section and build a database of commenters you can send beta invites too.
Most importantly. Good luck ;-)