Sometimes while working on a project, we get stuck. We run into a problem which we are not able to solve despite of trying for some time (a few days or weeks). Sometimes we don't even know what is causing the problem, and hence we can't find a fix.
This is a state in which all progress in the project is halted (till the problem is solved).
Is there a word/idiom/phrase to describe this state, or to say that you are in such a state?
I'll appreciate appropriate expression(s) in the context of programming projects, as well as those for any kind of project really.