It seems that my browser of choice is no longer working with Outlook Web Access for Exchange 2013.
Google has made changes to the latest version of their browser and removed the API ( showModalDialog ) which has serious consequences for managing a major parts of Exchange.
In my test I have noticed management options that I am unable to select also calendar options not available .
So now I wait for the Exchange team to provide a hotfix or update which patches this problem.
Back to IE for me.