Just noticed that in Mission Planner version 1.2.76 the Log Download function doesn't seem to work. I downgraded to 1.2.75 and it works fine.
If I select another type of frame ie. Rover or Plane then swap back to Copter it seems to help.
You are right, it's just with the new version.
this should now be resolved
Just Uninstalled MP, Downloaded new version & Installed 1.2.78 Build 1.1.5004.12827. SR0 SR3 Parameter descriptions are still missing. Just FYI Michael.