I think the best way out of that problem is to update Grace. Go to View->CCS App center, and then click on "See More" next to Code Composer Studio Add-ons, and then select the Grace update, and then Install software. That should install Grace 3 and XDCtools 3.30.03. Then go to Preferences and select these versions. Can you try that?
This thread explains why Grace 2.20 is not working well in CCS 6: http://e2e.ti.com/support/embedded/tirtos/f/355/t/354453.aspx