Geofield Display Format Data Options (Using Bounding Box)
i had the same problem and found a quick and dirty solution:
in the referenced file Point.class.php the following function throws the error:

  public function __construct($x, $y, $z = NULL) {
    // Basic validation on x and y
    if (!is_numeric($x) || !is_numeric($y)) {
        throw new Exception("Cannot construct Point. x and y should be numeric");
    }


adding "echo $x;" before the "throw" showed me the problem:
the numbers for $x and $y where in the wrong "local" format.

e.g. 9,34124 instead 9.34124

  public function __construct($x, $y, $z = NULL) {
    $x = floatval(str_replace(',', '.', str_replace('.', '', $x)));
    $y = floatval(str_replace(',', '.', str_replace('.', '', $y)));
    // Basic validation on x and y
    if (!is_numeric($x) || !is_numeric($y)) {
     throw new Exception("Cannot construct Point. x and y should be numeric");
    }


is my dirty fix for this...

regards
nicolaj