Wrong mysql_fetch_array


function author_info() {
$u_id = $_GET['id'];
global $tableusers;
$result = mysql_query("select user_nickname from $tableusers were id='".$u_id."'");
while($r=mysql_fetch_array($result))
{
$nickname=$r["user_nickname"];
echo "$nickname";
}
}

I get the following error:
Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in c:\serv\www\wp-content\plugins\profile.php on line 15
i’m using wp-profile.php?id=1
Does anybody see what i’m doing wrong? I sure don’t … i give up