html page hanging when posting file upload

I'm trying to add a file upload script in php to a website I'm designing. I've used an online example (I know it's not secure and I plan on making it secure, I just want the basic functionality working first).

Basically what's happening is that when I click the "submit" button, the page stalls and says "loading xyz server.." forever and doesn't ever go to the post action php page! This is very frustrating and I can't see why it won't work!

The code is below and I've tried this on 2 different servers with same results. I'd be very grateful if someone could let me know what I'm possibly doing wrong?

<html> 
<body>
  <form enctype="multipart/form-data" action="do.php" method="post">
    <input type="hidden" name="MAX_FILE_SIZE" value="1000000" />
    Choose a file to upload: <input name="uploaded_file" type="file" />
    <input type="submit" value="Upload" />
  </form> 
</body> 
</html>


<?php
//Сheck that we have a file
if((!empty($_FILES["uploaded_file"])) && ($_FILES['uploaded_file']['error'] == 0)) {
  //Check if the file is JPEG image and it's size is less than 350Kb
  $filename = basename($_FILES['uploaded_file']['name']);
  $ext = substr($filename, strrpos($filename, '.') + 1);
  if (($ext == "jpg") && ($_FILES["uploaded_file"]["type"] == "image/jpeg") && 
    ($_FILES["uploaded_file"]["size"] < 350000)) {
    //Determine the path to which we want to save this file
      $newname = dirname(__FILE__).'/upload/'.$filename;
      //Check if the file with the same name is already exists on the server
      if (!file_exists($newname)) {
        //Attempt to move the uploaded file to it's new place
        if ((move_uploaded_file($_FILES['uploaded_file']['tmp_name'],$newname))) {
           echo "It's done! The file has been saved as: ".$newname;
        } else {
           echo "Error: A problem occurred during file upload!";
        }
      } else {
         echo "Error: File ".$_FILES["uploaded_file"]["name"]." already exists";
      }
  } else {
     echo "Error: Only .jpg images under 350Kb are accepted for upload";
  }
} else {
 echo "Error: No file uploaded";
}
?>

Thanks very much for your time, I have searched for hours to fix this with no luck!

Solution

Nevermind! It turns out it was something to do with the wireless network at my University. I got home, refreshed the page and it worked fine. I will have to have words with the system administrator about the time I wasted trying to solve a problem made by them.

Thanks for the help anyway guys,

Scott