Ok, I've been (slowly) continuing my debug efforts, while I still don't have anything definitive, in light of what others are now experiencing, I thought I would post the additional information I do have in case anyone has any other ideas.
(a) It finally dawned on me that when the image is displayed (with the previously reported error message), ALL the slide navigation controls have disappeared.
(b) When I ran Firebug (the browser debug tool), I discovered the following error message being generated when I attempt to load the image:
fadeSlideShow is not defined
var phocagallery=new fadeSlideShow({ (line 7)
While the module (fadeSlideShow) appears to exist in the package, I haven't figured out why the system thinks it's not available.
(c) I checked the callback on what was being executed, and clearly there's a few things missing. I've got 2 images showing the tracebacks, but am not seeing how to attach them (it's getting late here), so here are the links:
trace_oldver.PNG - represents callback of the correctly functioning module
http://www.pnwexplorer.net/test/trace_oldver.PNG
trace_newver.PNG - represents callback of the incorrectly functioning module, generating the error reported
above.
http://www.pnwexplorer.net/test/trace_newver.PNG
(d) Thanks to the input provided by sgofferj, I ran some additional tests and here's what I found - if I go to PhocaGallery's Control Panel page, select Options, and proceed to "Detail View Settings" > "Detail Window" and change the setting from "Modal" to "Model (image only)", everything displayed correctly - without error. I then played with ALL the available settings for Detail Window, any of the following selections appear to function correctly:
Modal (image only)
Highslide JS (image only)
Shadowbox
Slimbox
Boxplus (image only)
All other options generated my original error.
And just to re-iterate, the only place I make any use of the sourcerer module is in 3 different articles, nothing where there would be any obvious interactions with phocagallery. I've not seen any other errors so far.