Office 365 error when downloading on Macbook Air

I have successfully downloaded Office 365 Small Bus Professional to a Win7 PC and my iPad. I cannot get it downloaded to my Macbook Air and receive the following message after I click Install. I reinstalled the O/S the other day and still get this error.

Server Error in '/' Application.

Runtime Error

Description: An exception occurred while processing your request. Additionally, another exception occurred while executing the custom error page for the first exception. The request has been terminated.