Mortgage rates reneged.

[Jerry Hill]

I am purchasing a new duplex and have been working with a lender. I've already completed the application and locked in my interest rate as of last week. I received a call this morning telling me that they had priced the loan wrong and needed to quote me a new interest rate. 

Is this allowed and do I have any recourse to hold them to the original pricing of the loan? Or do I just have to take what is offered? Do I have any negotiating power here?