I keep getting an error when doing a multi-city search on delta.com.

After doing a multi-city search and selecting the flights I want, I keep getting the error "We're sorry. The fare for the flights you selected just sold out. Please search again to view and select alternate flights." The fare I selected was economy cabin.

Is anyone else having this problem? (tech support was clueless, and in fact, hung up on me when I said I didn't want to book the flights, just wanted a price).

What can I do about it besides searching each segment separately and then adding the costs together (which isn't accurate anyway)?