The HMC987LP5E eval kit was working as expected and with the provided client software. Now the client seems to be communicating with the HMC987 eval board via the USB to SPI interface but will not affect the HMC987 configuration registers. I have swapped the USB interface card with another and everything is back to normal. When I switch back to the original USB interface card, it has the same failed response. What could have happened to the USB interface card? I have some other USB FTDI interface cards on some other test equipment being used for my configuration. Are they interacting and re-configuring the DLP2232M on the Hittite USB interface card? This is the second USB card to fail in this way.