You may need to target the entire .navbar-inverse .navbar-inner elements as follow:
.navbar-inverse .navbar-inner {
background-color:#ffffff;
background-image:-moz-linear-gradient(top, #ffffff, #ffffff);
background-image:-webkit-gradient(linear, 0 0, 0 100%, from(#ffffff), to(#ffffff));
background-image:-webkit-linear-gradient(top, #ffffff, #ffffff);
background-image:-o-linear-gradient(top, #ffffff, #ffffff);
background-image:linear-gradient(to bottom, #ffffff, #ffffff);
background-repeat:repeat-x;filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffffff', endColorstr='#ffffffff', GradientType=0);
border-color:#ffffff;
}
Regards,
Zulf