The problem I'm having might be related to this thread.
I use AHCI to boot Win7 Pro 64bit. My mainboard is a GigaByte ga-z68xp-ud3.
Recently my PC's power button broke, so being lazy, I disabled ErP in the BIOS, because that's necessary to get the Power On By Keyboard feature to work.
The side-effect of this is that the usbirtoy continues to receive power on USB even if the PC is powered off--I assume this is the case because I also realized that my plugged-in portable audio player continues to be charged after I shut down Windows.
Therefore, when I boot up again, WinLIRC gives me an invalid configuration error.
If I then physically unplug and replug the usbirtoy, it works again.