I keep getting the message ‘Cannot access installation media /download.opensuse.org/distribution/12.3/repo/non-oss/content’ Medium 1. How do I reconcile this? 
Can you please allways tell what version of openSUSE you use?
I assume that it is not true that you get that message all the time, but that there is some coincidence with the things you do. Like using YaST > Software > Software management or some other action. Please explain when you get this.
Indeed, some clarification would be helpful.
Last time I saw this was when Yast software management needed some dependencies in the install media, but it wasn’t accessible (DVD not in drive/pendrive not connected, broken DVD drive, etc.).
I think it was only a temporary problem accessing the default Opensuse repository during an update (apper ?)
I get some similar error from time to time. And it gets “solved” automatically when the repository is available again.
I don’t think you have to worry about it.