FWIW, whilst I locate my wife's video of this, here's my images of the same event in Lembeh in 2008 - not significantly different to Robin's. I couldn't work out how to insert the images, so just links for now (sorry):
http://www.flickr.com/photos/markatwell/3197881732/
http://www.flickr.com/photos/markatwell/3197035909/
Thank you for settling this! Robin and I were still 'heatedly' discussing it in Lembeh last week - July 2010! I thought it was struggling to slough its shell, and Robin thought it was 'crazed' by a parasite. At least honour has been served - we were both wrong! )
Mark