If you want to enable X++ debugging in AX 2012 you need to add the relevant users to the Microsoft Dynamics AX Debugging Users group under “local users and groups”, without so you will receive an error message stating:

the x++ debugger works only for users who are in the ‘microsoft dynamics ax debugging users’ local group of windows. Get added to the group then login again to windows.

This is no issue at all when installing AX 2012 on a regular server in a domain environment. 

But if you install AX 2012/R2 (although not recommended) on a server that is a Domain Controller – you will not find a local group as it cannot exist on a DC – In this case the group will be created in the ‘Users’ OU in your Active Directory and the relevant users must be added to this group via Active Directory Users & Computers GUI.

I have encountered this issue today and did not find any documentation on this specific scenario so I hope this might help someone 🙂

Good Luck