Disk Image for Mac is not working

Hi, 
I have been trying to install ProvToolbox using the given disk images for Mac. It downloads alright but when I click to install, it showed the error message stating that the disk image is corrupted and should be ejected. 
Any idea how can we solve this? In addition is there any other way we can install toolbox on Mac? 
Any help would be much appreciated. 
Thanks. 