webkit border radius question

Here's my problem: I'm showing an overlay (using this) with a message div that has rounded corners.

Here is my css code for message div:

#modal1
{
    margin-left: auto;
    margin-right: auto;
    display: none;
    width: 620px;
    height: 150px;
    position: relative;
    background-color: #FFF;

    border: 12px solid #FF771C;  
    -webkit-border-top-left-radius: 12px;
    -webkit-border-top-right-radius: 12px;
    -webkit-border-bottom-left-radius: 12px;
    -webkit-border-bottom-right-radius: 12开发者_如何学编程px;

    text-align: center;
}

And my problem is that I get a white "border" (if you look closely) in the upper left and right corners. Here is the image so you can see for yourself. Now, I "solved" this by putting top-left and -right border properties of webkit to 0px, but this is not a solution, so I'm asking if you have maybe some ideas? Btw, this is only developed for chrome that's why it's only -webkit up there in the code..

EDIT:

I found the solution on their forum http://flowplayer.org/tools/forum/40/46850

this seems to be the border of another div or element behind your rounded bordered div