This is a known issue in the Video Timing Controller v4.00.a.
This issue has been resolved in the Video Timing Controller v5.00.a and later.
The issue is that the Video Timing Controller v4.00.agenerates a behavioral wrapper by default, even though there isno behavioral model.
To work around this, users can generate a structural model from within CORE Generator.
Please see (Xilinx Answer 32754) for a detailed list of LogiCORE Video Timing Controller Release Notes and Known Issues.