Duh! And here I was thinking that I had messed something up big time!
- I have replaced the prettyPhoto files
- I flushed the permalinks (that expression made me smile as I feel my whole brain is flushing right now! LOL)
So far no success. I gotta run out the door right now but will come back later, clean the cache and follow further instructions based on your replies on this thread: http://www.kriesi.at/support/topic/wp-31-breaks-lightbox
Funny, I had seen that thread a couple of days ago and thought: I really hope this never happens to me... LOL ... and totally ignored the fact that new versions of WP require new actions!
I'm just thankful for you (and the rest of the support team) for keeping up with all the upgrades and having patience for all our [repeated] questions! ... ;-) Will be back later to report on this.