Something that pisses me off right now

I have gotten a small research grant. It is not a lot of money, but it is a "real" grownup research grant rather than student support, and it's the first time I have gotten a grant as an independent researcher. Two other people are involved in this project and since letting them know on Thursday that we got the money I haven't heard a peep. I have a strong feeling that the sudden silence is intimately related to the fact, that both are in the middle op writing up dissertations and at least one of the involved advisers is opposed to the person taking on more projects. I can see the point, but still, they are grown ups and my friends, and you just don't commit to something first and make other people spend their precious time and energy getting funding, only to wiggle your way out later. I have four weeks to accept or decline the grant, and I don't know what I'll do if these guys back out now.