If you're having the same issue as I was having then the solution that was posted should work. 

If so, make sure you right click along the top of the window that is unresponsive. Once menu box opens up, click Maximize. Then you should see the pop up window giving you the trouble. Close that window and you should be able to fully access Proseries. That is what worked for me. 

Also, a virtual machine is something I use because I am on an iMac. Since the Proseries software only works with Windows, I am using a virtual Windows operating system that is formatted for Apple's Mac OS. 

Good Luck!