I'm being told to fix an error in my federal tax return, but there is no dialogue box to modify or edit. Is this a bug with the TurboTax software?

You'll have to be more specific. When you run SmartCheck, and the error shows up on the screen, sometimes you can check the box on or off right there on the screen. Or read the question very carefully - sometimes it's unchecking a box. It can seem a bit tricky.