Julian,
Sorry, this was my fault and should now be fixed. Yesterday I upgraded some of the website software and it has broken the Gallery - please be aware that the Gallery is still broken and I am trying to fix that! As part of trying to fix the Gallery I put the site in "debug" mode and that reported the computerese you mentioned, which was caused by an issue elsewhere on the site. I have fixed that issue and the message no longer appears for me. Please let me know if you see any more warnings or errors, etc.
Jonathan