Are you using WiFi on a laptop to test this? Have you looked at channel utilization? What are you connected to, 2.4 or 5 Ghz? What does ICMP do (ping 188.8.131.52). Do you get all your replies or do you drop packets?
Do you have another network segment, maybe wired that you could use to test? Is DNS resolving hostnames reliably?
might be helpful to mention the software version of controller and the details of the web browser and whether you've tried it with other clients or other web browsers or whether you use a proxy, etc etc etc etc