Ok, so here is the error message I get when I when trying to use L and T on some C300 footage.
"CONTENTS" contains unsupported media or has an invalid directory structure. Please choose a folder whose directory structure matches supported media.
This is coming right off the card, out of the camera so there are no problems with file structure. Its happening with my C300 how ever my B camera (another C300) is loading up just fine. I then started going back through old cards that I have used L and T on my desktop with no problem, they are no giving me errors on my Macbook. It's appears to be a very random error. Cards all load up fine in XF Utility and can be viewed no problem. I can load the individual clips up into XDCAM transfer and they are there. The clips all seem fine but Log and Transfer won't seem them off my camera however an identical C300 does seem to work. It's more frustrating as this old card I tried from a few weeks back isn't working however is did work on my desktop so it proves there is no error with file structure etc.