Mettere hover al input type="submit"

[Ht28]

Ho già questo css, vorrei fargli caiore all'hover, ma qui è una cosa strana

#submit { 
/* Mette la sfumatura verticale */
   background: -webkit-gradient(linear, left top, left bottom, from(#ffffff), to(#b3b3b3)); /*Safari e Chrome*/
   background: -moz-linear-gradient(top, #ffffff, #b3b3b3); /* per Firefox */ 
   background: -o-linear-gradient(top, #ffffff, #b3b3b3); /* per Opera */
   filter: progid: DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#b3b3b3'); /* per IE6-7 */  
   -ms-filter: "progid: DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#b3b3b3')"; /* IE8 */
   width: auto; 
   height: 25px;            
   font-family: arial;
   font-size: 13px; color: #000080; 
   text-shadow: 0px 1px 0px white; 
   border: 1px solid #999999; 
   margin: 0 auto;  
   border-radius: 6px;                          
}


.manina-guest:hover {  /*Manina */
    cursor: pointer;
}

<input type="submit" value="Invia" id="submit" class="manina-guest" />