I tried that but it did not work.
I have questioned the customer support who asked for further information.
In the meantime, Roxio just released Toast 14.1, with a new version 1.0 (1) - a strange version number- of MyDVD.
And HALLELUJAH, I was able to create a disc image without crashing at 70 % of completion.
But ALAS, when I tried burning a disc, it crashes around 78 %, thus freezing the Mac completely (Mavericks).
So, Roxio is progressing, we just have to wait !