If I had to guess what's happening, it would be that the job turned out to be more complicated than they had assumed. As we all know, sometimes when you work on a complicated problem you're charting new territory and you don't know how long it will take to resolve it. They missed one deadline and they don't want to continue promising more deadlines that they can't keep. Alternatively, human factors such as an illness or having to work overtime could be a cause. Although having said that, I'm crossing my fingers like everyone else.