It has been determined that a software regression was introduced in ISE version 9.1i SP2 so that MAP sets PLL compensation incorrectly for DCM2PLL configurations. Compensation is incorrectly set to INTERNAL rather than DCM2PLL.
This problem is currently scheduled to be fixed in ISE version 9.2i.
Meanwhile, this problem can be corrected with the following user constraint (.ucf):
INST "pll_name" COMPENSATION = DCM2PLL ;