Background aparece e some!

Boa Noite a todos!

Tem uma DIV (#slider) que aparece a borda, mais nao aparece background de jeito nenhum, ja tentei background-color, background-image, ja mudei o z-index 1000 vezes e nada..

Sao 3 arquivos css, main-style.css (principal do site), detault.css e nivo-slider.css (ambos do nivo)

Quando eu abro o site da primeira vez, o background aparece por uns 0.5 segundos e some. ae quando eu atualizo (f5) ele somente pisca e nao aparece.

Qualquer ajuda eh bem vinda!

Obrigado,

Marcelo.

HTML

<div id="wrap-slideshow">
 <div id="slider" class="nivoSlider">

 </div><!-- /slider -->
</div> <!--/wrap slideshow-->

default.css

/*
Skin Name: Nivo Slider Default Theme
Skin URI: http://nivo.dev7studios.com
Skin Type: flexible
Description: The default skin for the Nivo Slider.
Version: 1.0
Author: Gilbert Pellegrom
Author URI: http://dev7studios.com
*/

.nivoSlider {
position:relative;
}

.nivoSlider img {

position:absolute;
top:5px;
left:5px;
display:none;
}

.nivoSlider a {

border:0;
display:block;
}

.nivo-controlNav {
position:absolute;
right:5px;

bottom:4px; / Tweak this to ajust bullets / } .nivo-controlNav a {

display:block;
width:22px;
height:22px;
background:url(../images/bullets.png) no-repeat;
text-indent:-9999px;
border:0;
margin-right:3px;
float:left;
}

.nivo-controlNav a.active {

background-position:0 -22px;
}

.nivo-directionNav a {

display:none;
text-indent:-9999px;
border:0;
}

a.nivo-nextNav {

background-position:-30px 0;
right:15px;
}

a.nivo-prevNav {

left:15px;
}

.nivo-caption {
 font-family: Helvetica, Arial, sans-serif;
}

.nivo-caption a {

 color:#fff;
 border-bottom:1px dotted #fff;
}

.nivo-caption a:hover {

 color:#fff;
}

nivo-slider.css

/*
* jQuery Nivo Slider v2.6
* http://nivo.dev7studios.com
*
* Copyright 2011, Gilbert Pellegrom
* Free to use and abuse under the MIT license.
* http://www.opensource.org/licenses/mit-license.php
*
* March 2010
*/

/ The Nivo Slider styles /

.nivoSlider {
position:relative;
}

.nivoSlider img {

position:absolute;
top:0px;
left:0px;
}

/ If an image is wrapped in a link /
.nivoSlider a.nivo-imageLink {

position:absolute;
top:0px;
left:0px;
width:100%;
height:100%;
border:0;
padding:0;
margin:0;
z-index:6;
display:none;
}

/ The slices and boxes in the Slider /

.nivo-slice {
display:block;
position:absolute;
z-index:5;
height:100%;
}
.nivo-box {
display:block;
position:absolute;
z-index:5;
}

/ Caption styles /

.nivo-caption {
position:absolute;
left:0px;
bottom:0px;
background:#000;
color:#fff;

opacity:0.8; / Overridden by captionOpacity setting /

width:100%;
z-index:8;
}

.nivo-caption p {

padding:5px;
margin:0;
}

.nivo-caption a {

display:inline !important;
}
.nivo-html-caption {
 display:none;
}

/ Direction nav styles (e.g. Next & Prev) /
.nivo-directionNav a {

position:absolute;
top:45%;
z-index:9;
cursor:pointer;
}
.nivo-prevNav {
left:0px;
}
.nivo-nextNav {
right:0px;
}

/ Control nav styles (e.g. 1,2,3...) /
.nivo-controlNav a {

position:relative;
z-index:9;
cursor:pointer;
}

.nivo-controlNav a.active {

font-weight:bold;
}

main-style.css

body{

background:url(../images/bg-body.png);
 font-family: 'Cuprum', serif;
 font-size: 16px;
color:#999;
}
#main{
background:url(../images/header.jpg);
background-repeat:repeat-x;
}

#header{
width:980px;
height:171px;
margin: 0 auto;
}
#wrap-slideshow{
width:100%;
padding-top:10px;
height:560px;
background:#fff url(../images/bg-slideshow.png);
position:relative;
}
#slider {
width:968px;
height:560px;
margin:0 auto;
position:relative;
border: medium solid #F00;
background-color:#F63;
}