Maybe the Sch C form is corrupt (Ive had corrupt W2 worksheets and 1099R worksheets in prior years that just dont work right)?   

Can you create a new Sch C and move all the figures over to it then delete the one causing an issue?  You can move any assets over to the new Sch C using the Change Activity option on each asset entry worksheet...yes its a bit of work, but less than starting over from scratch.