I found this message last night when I was trying to post a new episode of my podcast and found the same error.
Since I don’t have access to the file system on the site that hosts our wordpress, I wasn’t able to manually update the plugin.
I posted the episode anyway without the validation to see if it would work or not.
I thought others may be interested in knowing that everything still went out and posted to iTunes, etc. just fine without the validation.
So if you are confident in your URL format, it will still post using 7.0 of the plug-in.
You will still get errors shown at the time you post saying it can’t be validated, but it all still worked.
-Jesse Waldack
Nintendo Dads Podcast