Hi Friends,
Recently while importing model store in AX2012 CU4 environment, I got the below error:

To resolve this, run the axutil schema command.

After executing the axutil schema command, the model store import worked fine. If you are also facing such issue then worth trying this. It reinitializes the default model store.

More details regarding this can be found at the below MSDN link:
http://technet.microsoft.com/en-us/library/hh433540.aspx