Found this ...
I found this, thx for the suggestion.
If the DVD authoring program does not accept the MTS file, try renaming it with an MPG file extension. Most digital videos that contain an MPEG-2 data stream are distributed as MPG files. The format is more widely recognized than MTS.
(And I get the impression that DVD Flick is no longer maintained by the author?
I could be wrong, but the DVD Flick forums on the DVD Flick website are closed, inactive, unavailable.)