URL external source not working

I am trying to import data from some PHP scripts, which are gathering data from a MySQL database. When linking to one of the scripts (Link → Link to external data…) things works smoothly with no problem, I can see the ranges, choose the one I want and import the data.
The other script is not working at all. When trying to create the link there is nothing displayed, no ranges, no error, no nothing. So I took a look with my browser into the HTML source code resulting from both scripts. There is nothing to explain this behavior. How can I find what is going on?

Script 1 (working):

Script 2 (not working):

My environment:
OS: Ubuntu 14.04 with KDE
OS Version: Linux 3.13

Build ID: 8f96e87c890bf8fa77463cd4b640a2312823f3ad
CPU Threads: 4; UI Render: default;
Locale: ro-RO (en_US.UTF-8); Calc: group