It doesn't work for me too. In windows 8-64 bit i get the same error. Crack isn't working. I did what XenoCoder said, copied hole loader file where Action is installed ran the scrip and the same error occurs.
Mirillis Action! 1.16.3 Silent by M-K.rar (19.06 Mb)
here is the last choice for you guys to get it working! make sure that you have uninstalled completely the action app and reboot sys, then open program-files folder and look for Mirillis folder, if you can see it? , delete!
and now the final step , download the silent installer of action and double click on it, wait few secs till the shortcut was created on desktop, thats it! by the way the shortcut is already associated with the script, that means you cannot do something wrong now! if you got again this damn message? then radius have to change loader directory in the script.. or edit it yourself!