Is it not funny that you have no water because of a bad pool header?
Nice to inject a bit of humour into it Jeff thanks,
The good news is I have repaired the install and all is now working.
I reinstalled the nvidia drivers as per the bad pool header problem but this did not solve the problem. Then removed and reinstalled the orbx files still no go so indesperation got out my old back up drive and found after much searching a 3 month old terrain .cfg file replace the origional and again reinstalled orb x and all is now well. I also ran sfc /scannow to check the ms 10 file integrity.
Thanks ualini you were proved correct .
Also
jsapai for the url [why I removed and reinstalled an older version of the nvidia drivers]