As I knows, Wavelab isn't capable of loading VST-Instruments (VSTi) only VST Plugins, like Effects.
There is a difference between VST and VSTi !
On the other hand, what do you expect to do with a VST Instrument in Wavelab? Wavelab isn't a sequencer like software with the possibilities of recording data for controlling instruments. Wavelab also haven't any MIDI features (except MIDI Sample-Dumps) which are also necessary to play a VSTi.
Wavelab is a program to edit audio data, like wav files, and rendering effects to it.
To play VSTi softsynths, like Absynth, you need a VSTi hostprogramm like Cubase, Sonar, Logic or FLStudio4. Isn't that your dealer told you as you buyed Absynth?
regards.
Organix