You guys are getting things mixed up.
The hard line that is connected to the car has the flare. Behind that flare is a nut/fitting that screws into a rubber or SS line.
From your post, that nut/fitting is what is fubard.....correct?
The actual inner portion of the flare or brake line is not messed up......is this correct or not?
The rubber or SS line is what has the compression fitting in it. That is what needs to be replaced or looked at.
For the most part the brass compression fitting is softer then the hard line and will form a seal.
Do you have your old rubber lines? If so, put it back on and see if it still leaks. If it doesn't, you found your problem. Call the vendor you got the lines from and tell them one of the lines has a bad compression fitting and you would like a replacement. Or contact the manufacturer directly.