It's in the CSS Inserts:
Code:
div#imagecontainer {
margin: 5px 0;
border: solid 5px #666;
-moz-border-radius:10px;
-khtml-border-radius: 10px;
-webkit-border-radius:10px;
border-radius: 10px;
}
Just take off the border part. That should do it.
Wait...I just had a thought: this may show up only if you're using the ata-round.txt styles, which I imported. However, check and see if something similar is in your configuration.