Dirk,
Sorry to know that 6657 PCIE still didn't work with all the machines after downgrading FPGA, we tested with a Dell Precision T3500 and Optiplex 790 machine, they both worked. Let me try to find some models you used.
For building the IBL, what is your host PC, Win XP or Win 7? Thanks for so many comments, we will investigate.
Regards, Eric