Thanks again Marc. Turns out there was a problem with with my page being a dialog window. I removed 'data-rel='dialog'' from the button definition and I was able to make the successful call.
If one calls SPServices from a URL that looks like the following, I suppose it is not supported?
http://sharepointsite#&ui-state=dialog
If one calls SPServices from a URL that looks like the following, I suppose it is not supported?
http://sharepointsite#&ui-state=dialog