Object types missing from selection in Select Groups

we run our DC on a VM and it is exclusively used for DC and Certificate purposes.

this morning there was an application error with mmc.exe, so I rebooted the VM.

All was fine except that now when I go to add a user or computer to a group in AD, I can not select "computers" or "Users" when I click the object types button, they are just missing. The only two available under the select object types are "Groups" or "Built in Security Principles"  

I do not know why those object types are no longer selectable, but It is important that I get them back.

This is on MS server 2012 R2, up to date.