border-radius bug in Opera

A while ago I made a little page for myself and I stumbled upon a bug that I have since not been able to answer. When opening http://darngoodpictures.com/#showme you see navigation arrows on the left and the right side. These are completely CSS-made. Nowadays I would go another way, but it's done and I'm sticking to it :) In every browser I tested, the arrows looked like they should. The only exception is Opera. Opera renders the arrows in a way I have never seen before. Can anyone explain what is happening there? I figured out quite quickly that Opera has some issues with the border-radius-property of the arrows, but can anyone give more precise information? This behavior is so weird... EDIT: It is getting weirder and weirder. Originally I thought, my CSS in combination with border-radius somehow triggered the issue, but the problem IS border-radius. It gets intensified when border-width is combined with it. See the following jsfiddles: I: http://jsfiddle.net/62ujn/ (everything is rendered as one might expect) Key rules: ``` border-radius: 0; border-width: 200px; ``` II: http://jsfiddle.net/62ujn/1/ (first minor problems in Opera) Key rules: ``` border-radius: 50px; border-width: 200px; ``` III: http://jsfiddle.net/62ujn/2/ (up from here the rendering in Opera just gets ridiculous) Key rules: ``` border-radius: 50px; border-width: 200px 150px; ``` IV: http://jsfiddle.net/62ujn/3/ Key rules: ``` border-radius: 50px; border-width: 200px 150px 100px; ``` V: http://jsfiddle.net/62ujn/4/ Key rules: ``` border-radius: 50px; border-width: 200px 150px 100px 50px; ``` Strange. Very. Strange. EDIT 2: I just contacted Opera about this, as I suspect that there is no other answer than "Opera-Bug"... I'll keep this page updated when I get an answer that satisfies :)