Thanks for the replies.
@shooternz, Yes obvious checked before commenting 
Thanks for the tip, was not aware of the shift option.
This is Premiere CS6 issue, not OSX. It appears the 'issue' is saved to the project. Confirming, I am using the standard CS6 Keyboard commands.
I'm moving the current project between 2 machines and interestingly this afternoon, opening the project on the unaffected laptop, the issue appeared immediately & arrow keys failed to work. Shift-Arrow sorts it for now though.