My design is crashing during Related Packing. I have been able to determine that the crash depends on a KEEPER constraint in my UCF file. Is this a known problem?
This is a known problem that directed packing will crash when an I/O configuration is trimmed to the point where a circuit is reduced to just a PAD and KEEPER. This problem will be fixed in ISE 11.2 so that the PAD and KEEPER are also removed by MAP trimming. Meanwhile, the designer can either remove this I/O configuration or complete the configuration so that the trimming does not occur.