php codeigniter中的图片上传错误[上传路径似乎无效。]

I was using php codeigniter 2.x now i updated it to 3.x, after that my upload code is not working. this is my code. please go though it. when this code is working always getting the error

The upload path does not appear to be valid.

$this->load->library('upload');
    $session = $this->ifisSession();
    $uploadfolder = 'profileImgs';

    $fullPath = 'abc';
    $imageconfig['upload_path'] = $fullPath;
    $imageconfig['max_size'] = (1024); // 1mb file size
    $imageconfig['allowed_types'] = 'gif|jpg|png';
    $imageconfig['max_width'] = (1024 );
    $imageconfig['max_height'] = (1024);
    $fieldName = 'profileimage';
    //$uploadfilename = $_FILES[$fieldName];
    $uploadfilename = $_FILES[$fieldName]['name'];
   // printv($uploadfilename, 'this ihere');

    $fileinfo = pathinfo($uploadfilename);

    if (isset($fileinfo['extension'])) {

        $ext = $fileinfo['extension'];
        $imageconfig['file_name'] = $session['firstname'] . '_' . $session['user_id_pk'] . '_' . uniqid() . '.' . $ext;
    }


    $this->load->library('upload', $imageconfig);

    if (!$this->upload->do_upload('profileimage')) {

        $error = $this->upload->display_errors();
        $data['data']['profileUpdate_error'] = $error;
        // move to profile page with erro message
    } else {

        $profileUploadinfo = array('upload_data' => $this->upload->data());
        $profileimgurl = '';
        $res = $this->Model_userinfo->updateProfileImg($session['user_id_pk'], $profileimgurl);
        if($res > 0){
            $data['data']['profileUpdate_success'] = 'Profile Updated';
        }else{
            $data['data']['profileUpdate_error'] = 'Profile Not updated';
        }
    }