Using FPGA Editor to edit the DCM causes the DCM to not become LOCKED or not function correctly when the DCM is implemented in the hardware. When modifying the DCM in FPGA Editor, the tool drops some of the configuration parameter settings for the DCM when the DCM is modified and saved.
To work around this issue, you can set the environment variable XIL_SPECIAL_FEATURES = 1 before running FPGA Editor. If the environment variable is set, then the full DCM configuration settings will be retained when the DCM is edited, and the DCM can be edited correctly. For more information on editing the DCM in the 7.1i design tools, see (Xilinx Answer 21667).