Problem with saving an edit through lish/joe

Hi all, thank you for any help with this. It's something I've done many times with no problem, but not in a while, and I'm getting an error I've never had before.

I'm using a finnix installation and the Joe editor to make a change to my iptables file, and the editor won't save the change. I do my customary ctrl-k-x to exit and save, and instead of saving as normal, the return prompt I am getting is:

> cannot make backup file, save anyway? y/n/^c

I select "y", and then it says,

> error opening file

and does nothing further.

Another odd thing is that if I make a mistake and hit my ctrl-c for abort, and go back into the file in Joe to try again, it's then opening in read-only, and I have to reboot the finnix and remount the image to get back into the file in non-read-only mode. I've never had this happen before, either, and I don't know if that is important or related.

The only recent change on my server was closing an "open resolver" issue. It doesn't seem like that should have anything to do with this, but I'm mentioning it just in case.

So, any help MUCH appreciated, so I can just do my edit, save the file with the change, and have everything happy again!

Thank you.