Up until last night I was able to use "Dream Smoothing" (Artistic/G'MIC) but to my horror I found all kinds of messages this morning when I tried to use that filter again. Basically the messages amounted to "not found". I had a look on the G'MIC website and there too all references to Dream Smoothing were gone. How is this possible? Anyone any idea what might have happened? (there was no system crash or problem with my hard drive, and as I said, until last night Gimp/G'MIC happily showed me the filter)

Update: the same has happened with Iain's noise reduction, Finger Paint, and Colour Abstraction paint.

Did you do a refresh of your G'MIC? That would update all your filters. I haven't looked yet maybe thse filters were not being used as much and were taken off or given a different name.
You may be better to ask this question under G'MIC discussions too.

Same here. Refreshed and they are still there and I didn't have any trouble running them.
Same version to.

Sorry for posting in wrong area! Refresh did not work, ended up reinstalling both Gimp and G'MIC and problem has disappeared. Would still like to know what triggered it though, but will probably never know. Thanks for your replies.

David is moving some of the third party filters to a new location in the interface, and may require further interaction from users to access them (for security reasons). I'm sure he'll post here about it when he's ready.