Waves 4.0.5 is certified for panther.
>>If you are using G5 and/or Panther, you should download and install your bundle's update v4.0.5 from
www.waves.com > Download > Installers.
Obviously, you may have to download latest and greatest.
The "painful" (read: expensive) upgrade for me was from OS9-OSX. But that was long ago...