I found the error. Line 189 of gallery.js should be removed:
tb_init(‘a.thickbox, area.thickbox, input.thickbox’); // Fix bug, re-inicializa a thickbox
I’m not sure what bug it was fixing, but it caused a FF double display error. I tested the box on FF 2.0 and IE6 and it still works as it should.
I didn’t mention it before, but this is all for Ajax Gallery 3.0