Sound Card not detected after SPX2 Install

Long time user here. My DAW has Win 7 Pro (OS), and my sound card is a Mackie Onyx Firewire card (board is a 1620). I have been running this PC & soundcard for over a year, using Sonar 8 Producer 64 bit. No troubles ever. Note, no new hardware has been added or modified in any way in over a year. This morning I installed Sonar X2 producer, which I bought from the CW store yesterday (download version, which I burned on to DVDs to port the install files to my non-internet DAW). It installed just fine. However, Windows no longer recognizes that I have the Onyx FW sound card installed. I get the "no audio devices attached to your computer" error upon launch. I have tried everything... uninstalled and reinstalled the driver from the mackie site (I already had the latest anyway, but I figured it can't hurt to remove & reinstall). No dice. Reboot, uninstall & reinstall the driver, the installer always tells me "your device is now installed and enabled!" - yet, when I go in control panel - Sounds - Devices, I see "no audio devices installed". I must have reinstalled 12 times. Unplugged the FW cable, re-plugged, tried different sockets, the works. The only thing new was the X2 install. My PC & soundard have "behaved nicely" for over a year, no changes. So I know that it is not a chipset issue... it has worked for over a year! There is nothing but Sonar on the PC. No internet, no wireless, no network, dedicated DAW. Help!! I can't see why the PC would suddenly fail to recognize the card. Thanks for any tips. Ed