A case has been seen where map crashes on a Virtex design in 1.5i SP2. The problem is related to the packing of carry chains.
A work around for this case is to set the environment variable "XVKMA_NO_CARRY_CHAIN_PACK" which disables the map stage that leads to the crash. The workaround will cause increase in # of slices and possibly slower timing.
The problem is fixed in version 2.1i which is set to begin shipping at the end of June.