You might get this warning message if your design is using an advanced clock scheme that the classic timing analyzer does not support. The warning message can occur for example, if you implement your design with the Triple-Speed Ethernet megafunction and are using the Classic Timing Analyzer during compilation.
In order to avoid this warning message, do use the TimeQuest Timing Analyzer in the timing analysis process. The Classic Timing Analyzer was last supported in the Quartus® II software version 10.0.