Try this:
Uninstall WavePad, then remove a folder called "WavePad" from these locations:
- C:\Program Files (x86)\NCH Software\
- C:\ProgramData\NCH Software\ (if you can't find the ProgramData folder, set Windows to show hidden files and folders)
- C:\Users\<your username>\AppData\Roaming\NCH Software\ (if you can't find the AppData folder, set Windows to show hidden files and folders)
Restart the PC, reinstall WavePad from http://www.nch.com.au/components/wpsetup.exe
If the issue persists, enter a support ticket at http://www.nch.com.au/support/index.html