I've used SIG PRO 1.2 for years on my site, with no problem. I've recently updated JOOMLA to 1.5.19, using Rockettheme gantry framework. When activating SIG PRO 2, the pages that call for the plug in result in a "password protected" pop up box. You can see it here:

www.russbo.com/Contributors/sensei.html

The password protected thing does not occur on non SIG pages.

Also, my thumbnails don't show, but the images do show when the gallery is clicked on, and the engine presents the various images.

As this was working fine with SIG 1.2 (on older, non gantry, version of Joomla), I'm baffled.

I know this is probably a permissions problem, but all the necessary areas (cache, images/stories/temp, temp, are 777. and no thumbnails are being generated in the temp directory, but I see them in the /cache. Not sure why the initial one is not showing up in the article.

Pm me access to your backend please.

Your www.russbo.com/cache/ folder is password protected (perhaps by accident). Remove the protection to restore normal functionality for your joomla site.