The first thing I'd do is create a new project and try running it with no changes at all. If that works, make changes to it so it is like your current project and see if it will run. If so, there's must have been something corrupt but it was basically a one-off and you can ignore it unless it recurs regularly. If not, it must be something to do with your changes so you need to start making changes one at a time and see exactly which change makes it break.