A question/problem for my Mac system friends.

A few weeks ago Time Machine backups of my internal hard drive started failing. The error message (which is no longer available so I can't quote exactly) says that I should check the disk that I'm backing up to. I did, with Disk Utility. It's okay.

So I did a backup with another disk, and another, and another. I even bought a brand new disk, formatted it freshly, and the backup there failed too.

So I conclude that the error message is lying, that the problem isn't with the media I'm backing up to, it's the source disk that has the problem. So I checked it with Disk Utility. It says it's fine.

So now I have a conundrum. I wanted to do a backup and then start using the new drive as my boot disk. But I obviously cannot do that. Unless one of the brilliant people who reads this has an idea what I can do to get one good backup from the internal disk, before saying sayonara!

Any help much appreciated. 

PS: Yes I know I can start over from scratch. No need to suggest that. Thanks.

PPS: I decided to start over from scratch. It's working out pretty well.