All .js and .jsx files are listed in the Scripts menu.
The SimpleViewer.jsx file (listed as 'SimpleViewer') is the actual plugin and it is this entry which should be selected.
The simpleviewer.js file (listed as 'simpleviewer') is the JavaScript file used internally by SimpleViewer when the gallery is displayed (and this is not the plugin and should not be selected).
The 'simpleviewer.js' file can be hidden from the Scripts menu by prefixing it with a ~ characters. Then, only 'SimpleViewer' (the actual plugin) should be visible.
This has been already been done with the SimpleViewer-Standard JavaScript file (which the plugin comes bundled with) but when you upgrade the plugin with your SimpleViewer-Pro files, you will need to rename the new JavaScript files manually.
Go into the plugins's 'svcore/js/' folder and do the following:
(1) Rename 'simpleviewer.js' to '~simpleviewer.js'.
(2) Rename 'swfobject.js' to '~swfobject.js'.
I have now added this information to the Upgrading the Photoshop SimpleViewer Script support page.
Steven Speirs
SimpleViewer Support Team