Sounds like you have magic_quotes_gpc enabled on your host.
function sanitize($value)
{
if(!is_numeric($value))
{
if(get_magic_quotes_gpc())
{
$value = stripslashes($value);
}
$value = "'" . mysql_real_escape_string($value) . "'";
}
return($value);
}
$query = sprintf(
"INSERT INTO table1 (col1, col2, col3) VALUES (%s, %s, %s)",
sanitize($_POST['value1']),
sanitize($_POST['value2']),
sanitize($_POST['value3'])
);