Slimbox 1.3 and Lightbox 2.8.2 not working with Atahualpa 3.4.1

Slimbox works fine with Atahualpa 3.2, but doesn't with 3.4.1. I've tried Slimbox with Wordpress Classic 1.5 and that works OK. I have the same problem with Lightbox 2.8.2.

When I click on a thumbnail the image opens in a new browser window, rather than the Slimbox effect.

Here's an example using Slimbox and Atahualpa 3.4.1:

http://escapetocontinue.co.uk/blog1/