Found a fix on osc2nuke forum
I'll post it here also for maybe other osc2nuke users who got this problem like me...
chipjack wrote: › Gallery uses a PHP variable named $breadcrumb. OSCommerce uses a variable by that name as well. Hence - conflict
decided to patch up Gallery, rather than osCommerce. Here's what I did:
in the following files:
search.php
slideshow.php
slideshow_low.php
view_album.php
view_comments.php
view_photo.php
layout/breadcrumb.inc <--- note, this is in a subdirectory
replace all occurances of "$breadcrumb" with "$gal_breadcrumb"