[quote user="mattcrowther"]Think I transfered everything over using the HDD cable when I got the new machine last christmas, though as have had internet access until now had not noticed any problems.[/quote]
If the new console was never connected to Xbox Live before, maybe it never downloaded any content and thus doesn't show up in the DRM tool. So you could be trying to transfer your licenses to the old console ID,
which is where they started in the first place... On the License Transfer page, compare the console ID(s) listed to the one shown in your current console's System Info. If the current console ID isn't shown on the web, you can get it there by downloading a
free game trailer or gamerpic or something.
The other possible problem is that you did the web part of the license transfer but did not re-download all your content to finish the re-licensing of it. (Transferring via cable from your old HDD is not the same
as re-downloading for DRM purposes.) Since the License Transfer can now be done every four months, you wouldn't be getting the previous error of not being able to do the transfer again 'til December, 2012. Since your current console is now connected to Live,
you could try re-downloading some bit of content (that wasn't working offline) and then try it offline again. But the console ID verification should tell you for sure.