TOAST.. PLEASE HELP US WITH DISC BURN PROBLEM!!

WE have been successful in burning Blu Rays in the past using Toast. Now for some reason, we have edited this years holiday using iMovie 10.1 and the actual project is a little over 2 hours long, and includes Canon Camcorder footage, Canon EOS photos, Go Pro 3+ footage and another Canon compact camera photos. The encoding has taken roughly 3 hours, which we don't mind, but in the final process we keep getting this message... THE FILE 00001.M2TS COULD NOT BE ACCESSED, DATA FORK, -42.

Now can someone please explain firstly what this means, and can I fix it, do I have to do something with Toast or download a file or WHAT!!!!!!

This is really frustrating as we have been able to burn Blu Rays in the past, but for some reason or another, not this time. We are even looking at downloading an app from the App store to create a blu ray (yet more expense). We have already uninstalled and re-installed Toast, but still get the same error message and Toast then tells us that the burning of the disc cannot go ahead due to an error and has failed.

I know Toast is working because we burnt a 5 min video onto DVD and that went without any problems. We have also tried to split the project into two parts, an hour long each part, but still no success.

Any help please in basic speak, we are not that technically minded would be appreciated.

Thank you...😠😠