Hi again,

I finally found another solution to get my job done, so I come to post it here, could be usefull for many users I think....
I think it's also easier, with less code to edit.

First, I found this thread that I used as base. But it wasn't fitting my needs of a slideshow.

Then, I installed another slideshow plugin : Smoothgallery2.

I changed in the jooblogs hack :
joogallery src=[media/k2/galleries/'.$itemGallery.'
with :
smoothgallery folder=media/k2/galleries/'.$itemGallery.'

It still wasn't working, so I tried William's idea to deactivate mootools with the plugin he told me to use. It worked !

Finally, a little bit of CSS editing in the Smoothgallery plugin, and it was done !

The only problem, is that I found only one transition effect for now on, I'll come back to post here if I find some more.

Hope this will be usefull,
Best regards,
David aka Shapes

@Shapes,
Great solution! thanks a lot, I followed your instructions and it worked! Had to fight a bit couse your code line is not precise, but it works! With one disadvantage: the gallery does not hide when there is no Gallery attached to K2 Item, it stays there endlessly loading something on black background. If you have work around for this that would be great!
thanks again,
krmr