Add the SIM_DEVICE attribute to the instantiation of the RAMB16BWER primitive in the pcie_bram_s6.v[hd] file.
This is found in the generated core's source directory.
Add the attribute and set it to "SPARTAN6".
Note: "Version Found" refers to the version the problem was first discovered. The problem might also exist in earlier versions, but no specific testing has been performed to verify earlier versions.