The themes I use include popup2-2.1.4, xPopup-2.0 and xpopup-2.0.3. Can't say if any one of those is specifically the cause.



Sure, will do.

I did remember to mention that the point of the exercise is not promoting some new piece of software made by ME?

The point is that any (new) user
- must be told
- right at the start
- immediately visible
- and without any further doc-reading
- that an Update (not necessarily an updateR)
- is absolutely mandatory and is not a question of "option" or "later"

Obviously that I cannot do because all I can do I post some textlines somewhere in the Downloads section.

But even on that page that will be nowhere near any point where the new user will immediately see that he absolutely must update.

This is not a software-issue. The software is fine, even counting a few small and unimportant quirks. It is the issue of getting people to know some very few but important infos.