That's odd. It worked perfectly for me in firebug. In fact when I visit your site right now, that's what I'm seeing. A 2px border in colour #cecece. And here's where my head is at:
MEET THE TEAM</div>
<img width="176" height="103" alt="" src="http://www.moko.com.php5-21.websitetestlink.com/wp-content/uploads/2011/07/MOKO_home_meet_the_team.jpg">
The images reside within the div class ".dividerpress" Why? I dunno. They just do. :-)
Clear your browser cache and try rechecking your site, because the border on the images is no longer black when I look at it from my end. It's 2px and #cecece. It also appears that you may have added the change to the galleryview.css instead of your themes css as I suggested, but that's up to you.
Good luck with it!