Try moving the Preferences folder to a backup location; when Wavelab starts again, it should recreate the preferences. You will lose any special key commands and other settings, but you can put individual files back until you find the corrupt file causing the problem.
Often the problem is the General.Dat file. Start by removing that to a backup location and see if that fixes the problem.
(The folder is in Users//AppData/Roaming/Steinberg/Wavelab 8/Preferences if you are using Windows.
On a Mac, it is in the Library folder somewhere…