For CoolRunner XPLA3 and CoolRunner-II designs, the Summary tab values initialize to "0" after loading a design. This does not match up with the power values listed in the power report file.
Select any field in the XPower GUI, and press the Enter key. This causes the Summary tab to refresh with the proper values.
This problem has been fixed in the latest 6.1i Service Pack, available at:
The first service pack containing the fix is 6.1i Service Pack 1.