Try setting it to "5" in the inner portal menu. Then go into your IPTV stalker portal, go to settings, and set it to "500" . Return to the main menu (inner portal) and reboot.
This seemed to help me when I use WiFi. I notice no difference when plugged in with LAN cable.
Edit: Make sure you go into the system menu and do an update (there is a new update on MAG update server, came out a few weeks ago) make sure you have the latest.
Cheers