[Porsche-O-Phile]

In addition to payment milestones, it's a good idea to build "phasing" into projects whereby either the client or the contractor has the right to discontinue the relationship once the conditions of that phase are completed. I do this on my design contracts - it gives you a chance to say "thank you, here's what we agreed on, I recommend you find someone else to pick it up from here forward and I'll provide them with whatever background information they need" to a problem client. Similarly it gives the client the right/opportunity to find someone else if they're dissatisfied with me after doing Phase I.

Assuming that's not the case, I'd review your contract carefully. Do you have the right to terminate contract for non-conformance to timetable? If so, you could possibly consider kicking them off the job and finding someone else, but (1) that's messy and (2) the "new" G.C. might not be any better.

Best of luck.