Garden Gnome Software offers the following products:

Pano2VR Panoramic image converter for Windows/Mac/Linux	Object2VR Object movie software for Windows/Mac/Linux	Pano2QTVR Panorama & object movie software for Windows only
Current Version: 2.1.0, 2008-09-21	Current Version: 2.0 beta, 2008-10-02	Current Version: 1.6.6, 2007-07-30

What is the difference between Pano2VR + Object2VR and Pano2QTVR?

In short: Pano2QTVR is the older product, runs only on Windows and depends on Apple's QuickTime. Pano2VR and Object2VR have been completely rewritten, run on Windows, Mac, Linux, and doesn't depend on QuickTime (hence the changed name).

You can find a detailed comparison on the features page.