My system (Win7 and Scope - Creamware soundcard) has worked fine with wavelab for the last few years. Only recently this error message has appeared, and no way to re-assign soundcard in preferences - as wavelab will crash. Cubase still works fine, and there’s been no software updates for the soundcard over the last five years.
Erase this folder:
C:\Users[yourname]\AppData\Roaming\Steinberg\WaveLab Pro 9.5\Presets\VST Audio Connections
Can you start WaveLab now?