mdgm is right about the filepath, you have to use "/" instead of "\". At least, those are the ones I have in my settings.json and my Transmission is working.
As for the shares:
You c-share might've disappeard because you aren't logging in via CIFS as admin. You only see the c-share when you're logged in as admin.
That you see only a folder names "transmission" in you media share would suggest you were either using the wrong filepath, since you state you were using \c\media\BitTorrent, so there would be no transmission folder. The other option is that you are using Radiator 4.2.19 and (re-)installed an add-on that messed up your share settings.
This last option is solved by installing the latest beta of Radiator, found here
I'm not sure, but I think you can get your old share-settings back by renaming or remaking your shares in FrontView. There's a post on this forum about that somewhere...