Hmm, yes that would help me tremendously but, dealing with a live site, I really can't think of doing that just yet.
The thumbnail attachment is just an image attribute used in my article class where I can upload an image directly from my desktop etc without first placing it first in the media folder.
Bill - you can activate debug with limitations. For instance, you can use DebugByIP setting to enable it only for a range of IP addresses, or you can enable it by UserID (depending on your eZP version). That way, you only see the debug output when you are logged in (no one else would see it, even if they are logged in).
The other thing that would help is to use
{$content_version|attribute(show,2)}
to see where the attribute call is failing.
There is an extension that allows you to do this in debugoutput which is very helpful - it is called Dynamic Debug.