Thanks for suggesting a look at the (Firefox) error console. I received a message "window.open is not a function", Googled, and the 3rd result led back here to: viewtopic.php?f=7&t=8453
I should have read the "General troubleshooting" suggestions at viewtopic.php?f=7&t=1431
because pressing the Reset button within the NoScript options has fixed the issue when using 2.4.3 !!!
(Is it strange that reverting to 2.3.4 also restored the pop-outs?)
Thanks for making the web a safer place,