last menu item hover border different from others

Hi,

I’m using the following code to hover a 2 pixel border under active menu items. I’ve used this code on many sites now but on this one: http://hpltechnology.com/ the last menu item (and it’s always the last menu item) is showing a 3 pixel border with a white inner.

.avia-menu-fx { border: 2px solid #000!important;}  /*change thickness of menu hover bar*/ 
.main_menu {padding-bottom: 2px!important;}

I’m totally baffled as to what is causing this as it’s always the last menu item so not a specific page and it’s exactly the same code I’ve used on many sites.