Windows Home Sever won't backup

So, that happened…
One day my WHS just stopped backing up my main system. The one in the kitchen (with nothing of importance on) it still backs up. It warns that the backups are out of date, but offers no reason or suggested solution.

If I try a manual backup it fails at 0% after a long wait and the error message says a drive might be faulty and to run CHKDSK. Doing that through Win 7 works on all but one drive - it asks if it should force and unmount and then nothing.
So perhaps this is the culprit, but excluding it from the backup doesn’t help.

Any clues on what to do, how to find out if anything’s wrong with that drive and whether that’s the reason. I’m stumped.

Are you getting the drive fault on the WHS or on your main system?

Also, did you try reinstalling the WHS client from the server/software share?

Dumb question, but can your main system still “see” the WHS? Is there a shared folder or something you could access on the WHS from your main system to see if it’s got a valid connection?