OK spent quite some time searching the KB without success. I tried several uninstalls and reinstalls without success so I uninstalled the 767 as well and did a system restore to the day before.

I then installed the 727 ran and tested it in FSX OK after which I installed the 767 and tested it. Both coexist without problem now.  :)

I initially installed the 767 and then the 727 consecutively without starting FSX in between, the actions must have created a fault.

Live and learn, hope this helps someone with a similar problem.  ;)