The Frozen Interface is usually set on block symbols in the design (composites) to prevent accidental update to the interface. These appear as local symbols in the DxDatabook - CL View - Symbols section. You unfreeze them by selecting an instance in the schematic and using the context menu on the right mouse button. Make sure you select the right instance when doing this if you have more than one instance of the same block in your design.
If they really are in the library then respond to this thread indicating how they got in there.