Hay everyone, sorry for the bump...
I'm new here and have the exact same problem.
Even with openned "tutorial" files already in Construct, i simply can't preview the game at all.
Always giving me this
can't find localhost:50000 adress etc..
I tried changing port to 50001 or 50100 or between. Changes nothing.
I run on the free version of it on steam. (can't download the standalone from scierra.)
and with latest drivers browsers.
Anyway, my computer is very clean and stable with any other application.