The thumbnails in both galleries look identical to me (and from your code, it looks like they should be identical).
In your http://treeserviceworcesterma.com/gallery1/ gallery, your thumbURLs are invalid and the gallery uses the imageURLs instead.
In your http://treeserviceworcesterma.com/gallery1-test/ gallery, your thumbURLs are valid but point to images identical to the imageURLs in the first gallery.
You might find that your thumbnails look better if they are displayed at their actual size, so rather than use 700 x 525 images (as your http://treeserviceworcesterma.com/gallery1-test/ gallery does), try using dedicated thumbnails at the thumbWidth and thumbHeight dimensions used in your gallery's XML file (100 x 100).
If using svBuilder to create your gallery, thumbnails will be generated for you (from your original images) at the specified size and the appropriate thumbWidth and thumbHeight values will be set in the gallery's XML file.
SimpleViewer Support Team