You can maybe find this error message when you using a clustered SQL Server.
You cannot create/delete a new model (from AX client or from AxUtil.exe tool) but can still make a listing of all model.
In fact, all writing modification cannot be done.
So if you are in this kind of problem, the first things to make is to check on all nodes of the clustered server if the following port are open (and check also in the client side) :
- Remote Registry: 139
- Remote administration: 445
Check correctly the setting of the firewall !