Código HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<script language="javascript">
function cambia(color){
var letra;
if(color == 1)
letra="000000";
else
letra="FF0000";
var objeto = document.getElementById("tabla");
objeto.style.borderColor = letra
}
</script>
</head>
<body>
<table id="tabla" width="200" border="4" bordercolor="#FF0000" onmouseover="cambia(1);" onmouseout="cambia(2);">
<tr>
<td>a</td>
<td>b</td>
<td>c</td>
</tr>
<tr>
<td>d</td>
<td>e</td>
<td>f</td>
</tr>
<tr>
<td>g</td>
<td>h</td>
<td>i</td>
</tr>
</table>
</body>
</html> A mi me funciona bien...