Backup not working and test connection made home page blank

I have been happily backing up one Pro 6 to another for well over a year, using standard backup of C of ReadyNas 1 to backup share of ReadyNas 2. This essentially created a mirror image.

For some reason unknown to me this stopped working. I think it was because ReadyNAS 2 became almost full. I cleared out some other data and expected backups to resume but they did not. So I went into ReadyNAS 1 setup in Raidar and clicked the test connection button. It generated an error message saying it could not connect (though both NAS's show up in Windows Explorer in the Network section and I can access contents of both on my computer).

I did a bit of reading and read about RSync. This seemed like a good idea so I changed the backup settings on NAS 1 to Rsync rather than the normal backup. I clicked test connection and got the "working" revolving cog symbol which never stopped. I could not get the Raidar NAS screen to react in any way to clicks anywhere so after a while I closed the window.

On rerunning Raider and clicking set-up for NAS 1 I got a ReadyNAS home screen page as usual which has the yellow bar at the top and the word ReadyNAS and Refresh, Help, Logout and Apply buttons, a copyright notice and six green lights at the bottom, but it is blank in the middle, just a big white space.

I tried shutting down NAS 1 manually and restarting but the problem remains. I can still access NAS 1 and view files via Windows Explorer, and see the usual info in the Raidar startup screen, but as soon as I press Setup I get the blank NAS home page. The home page for NAS 2 is fine.

Can anyone suggest what has happened here and a solution?

Thanks

Peter