file is locked, not editable

I am not able to edit an existing .rtf file after upgrading to Yosemite. It says the file is locked, and when I click on the "save anyway", it warns me that I don't have the permission. I am the administrator on my iMac, and I have read&write permissions on this existing file. The Get Info does not indicate that it is locked, and it also indicates that I have read&write permissions.

How do I make the file editable again? I was able to edit the file before upgrading to Yosemite.

Do I have to be concerned about all my files not being editable now with the Yosemite !?

thanks,

Al