Designs that utilize an input that drives the D-input of an ISERDES as well as the combinatorial route-through path into the FPGA fabric will cause BitGen to generate an error message similar to the following :
"ERROR:BitGen - Failed to program routethru in site ILOGIC_X0Y200 for driver pin = D and load pin = O"
The ".bit" file that is created is functionally valid with the exception of the above-mentioned paths.
At this time, there is no way to work around this issue. Please open a WebCase if you encounter this issue and need further assistance.
This issue will be corrected in ISE version 9.1i.