I've been using VRWorx since 2001, and I've been generally happy with it. The last update, however, made it rather picky about the image sets that it would be happy to work with. Where the previous versions would produce good results with a hand held camera and an unknown focal length, the latest version appears to be rather strict about the settings you give it.
Today I started playing with the OSX version of Hugin, which while also very picky about some settings, will try to stitch anything you give it. sometimes in amusing ways.
Anyway, I've figured out how to coax it into stitching together a little three image panorama I took today, which VRWorx choked on.
Now to try to get it to make sense of the 12 image one I took as well.