... I can report that having re-downloaded the LR5 series today Friday 27 December 2013 all the files now open and at least start play with QuickTime, and I am no longer getting the "Error -2048" dialog that I believe was associated with the DRM. ...
Glad you got it sorted out. I firmly believe that 99% of the reported problems can actually be sorted out fairly easily - if the customer chooses.
The frustration for customers (and also for me) is that the system does not operate exactly the same way that it used to.
As someone in the software industry has said, "Everyone wants their software to improve; no one wants it to change!"
That is easily understood but often hard to execute when adding features.