UPDATE 2: Removed Microsoft USB receiver thing that was not in use. Unplugged and replugged dongle. Saw WaveLab splash screen for both 32 and 64 bit. But that was it. Replaced Startup.ini again. Still nothing.
What do you mean with “Still nothing”? Problem solved?
From the log, I can imagine a problem with some directory pointed by the WaveLab file browser.
Try erasing this older;
AppData\Roaming\Steinberg\WaveLab Pro 9\Cache
and this file:
AppData\Roaming\Steinberg\WaveLab Pro 9\Preferences\General.dat