[Plugin: NextGEN Gallery] Message to install flash where there used to be a slideshow

I’m running a NexGen-Gallery slideshow in a widget at https://theagnonschool.org.

I can see the slide show fine on all my different computers and in different browsers. And last week my clients were able to see it too.

But this week my clients can’t see it from their work computers (Windows XP, IE 8). They see instead a message to upload or upgrade Adobe flash.

I don’t think I did anything to the site that affected NGG over the weekend. Anyone have advice for me?