When I select "Show I/O Banks" in PACE, it causes a "FATAL_ERROR" message.
If using PACE to place I/O's, this issue might occur. In the FPGACORE, there is only one I/O standard, so this feature is not necessary for I/O placement. To work around this issue, use the Constraints Editor, which does not use a graphical interface.
This issue will be fixed in the next major ISE release.