Resizing image with php works with small images but not large

Here is my problem

If I upload a picture using a picture at 1024x768 at 112k the image is
uploaded fine and the thumbnail is generated fine.

If I upload a picture at 2333x1750 at 2mg the original file is
uploaded fine but the thumbnail is not created. Anyone know why?

My php is set to upload files at a max of 8 megs so Im not sure as to
why the thumbnail on the larger image wont generate.

<? include ('connect.php'); ?>
<? session_start(); ?>
<?
if ((isset($user_logged) && $user_logged != "") || (isset($spassword)
&& $spassword != "")) {
$userloggedin = true;
}
if (isset($userloggedin)) {
$mktime = mktime();
$idir = "/pics/member_images/$user_id$mktime"; // Path To Images
Directory

$copy = copy($_FILES['imagefile']['tmp_name'], "$idir" .
$_FILES['imagefile']['name']); // Move Image From Temporary Location
To Permanent Location
// Specify your file details
$current_file_nodir = $user_id.$mktime.$_FILES['imagefile']
['name'];
$current_file = "$idir" . $_FILES['imagefile']['name'];
$max_width = '500';
// Get the current info on the file
$current_size = getimagesize($current_file);
$current_img_width = $current_size[0];
$current_img_height = $current_size[1];
$image_base = explode('.', $current_file);
// This part gets the new thumbnail name
$image_basename = $image_base[0];
$image_basename_explode = explode('/', $image_basename);
$image_basename_after_explode = $image_basename_explode[6];
$image_ext = $image_base[1];
$thumb_image_name = $image_basename_after_explode.'-th.'.
$image_ext;
$thumb_name = $image_basename.'-th.'.$image_ext;
// Determine if the image actually needs to be resized
// and if it does, get the new height for it
if ($current_img_width > $max_width)
{
$too_big_diff_ratio = $current_img_width/$max_width;
$new_img_width = $max_width;
$new_img_height = round($current_img_height/$too_big_diff_ratio);
// Convert the file
$make_magick = exec("convert -geometry $new_img_width x
$new_img_height $current_file $thumb_name", $retval);
// Did it work?
if (!($retval))
{
$sql = "INSERT INTO memberimages VALUES
('','$user_id','','$thumb_image_name','$current_fi le_nodir')";
$result = mysql_db_query($db,$sql,$cid);
echo '<script type=""text/javascript"">history.go(-1);</script>';
}
else
{
session_register("error");
$error = "Unable to Upload the Image, Please try again.";
echo '<script type=""text/javascript"">history.go(-1);</script>';
}
}
else
{
echo '<script type=""text/javascript"">history.go(-1);</script>';
}
} else {
session_register("error");
$error = "You need to be logged in to upload your avatar.";
echo '<script type=""text/javascript"">history.go(-1);</script>';
}
?>