bul, opes prime and anz overhang

I hear this bought up quite regularly as a hard to exactly quantify yet potentially serious impediment to the SP progress of BUL. Without going into too much or too little detail, why is it (an impediment to the SP progress of BUL)? I'm broadly aware that ANZ ended up with large chunk of BUL shares after Opes Prime blew up. Couple of paragraphs would be nice. Thanks.

karoshi.