Thank you John,
it's all very strange.
I tried something in Montage Center last week.
Cannot remember particularly what I was doing but, the program either crashed or closed down normally, but now the program will not start.
It is a stand-alone program, so should run okay without TC loaded.
Which is normally the case.
It appears it is looking for something to load/open but cannot find it.
What this could be I have no idea.
Perhaps I'll just go back to using Adobe Premier pro.