I have the same problem with the VA12a. I just get a blank flashing screen.
I have been dealing with X10 support since Jan09.
I am on my third return va12a. still the same.
For the first one I could not get the drivers loaded.
I have uninstalled, cleaned everything from the registry, unloaded the AHP drivers. Several times
Re-downloaded the VA12 drivers, and this time it at least loaded the drivers in the correct spot.
I have tried to get it working in Safe Mode with networking, tried USB2 ports on a separate usb(Belkin) board, on a powered USB2 hub, on USB1 and USB1 powered hub. Same results.
I had the VA11 working before I tried the VA12a.
I am running Winxp Sp-2.
I also have an ATI All-in-one card for graphics.
I get X10 support to trade emails and phone calls for awhile and then they disappear for a few weeks until I start buging them.
I did get to their senior support but it never got fixed.
The one thing that the senior guy told me was that the Va12a drivers in Device Manager show up under "Sound ...." NOT under "Imaging devices" like the VA11 does.