troubleshooting with lightbox2 module

Hi
Thanks for this module
I have some nodes with slider are displayed in a lightframe from a teaser image.

It seems there is a troubeshooting with this use : sometime (and i didn't manage to get a regular behaviour), the container's width (#slider .scrollContainer) is set to 0. This do that all slider div overlap (see attachment)

So after have a look on the slider.js file, it seems sure that the problem comes from line 19

 // calculate a new width for the container (so it holds all panels)
    container.css('width', panels[0].offsetWidth * panels.length);

one of the two values is calculate to 0, but i don't know why.

It may this behaviour is due to usage of cache system as i have the first troubleshooting with boost module, but i manage to reproduce it without the module (and on a new installation) even with cache page disable (but not content cache). Cache is yet suspected because it only happens with anonymous user (i have to try with a simple user, in fact i just tested it with user 1 and anonymous) and a cache clear (with admin menu or drush) help to have the correct behaviour.