"my friend has the same model tv and his apps work just fine."
That's a clue. Compare their internet service and router to what you have. Also, forget the WiFi connection while you work on it. In fact, disable WiFi on the router as you could have folk mooching your internet connection and causing speed issues.
This is not an offer to cover the mooch issue in detail. That should be done in it's own discussion on an appropriate forum.
I bought an Samsung led tv 55inches 7500 series and two particular apps don't work from day one after I installed them. The fitness vod app keep buffering and eventually fail to load and show a message" cannot load data, check your network status. The time tv app always show a message" the application is not available due to network error" . I have called Samsung support 4 times and was told to do all those things include hard reset on the tv and smarthub, changing the DNS setting to 8888.All these won't solve the problems .The firmware is also updated. I have a wired connection and all the other apps work fine. Some Samsung rep even suggest the particular site are under construction or updating. I know it's not true because my friend has the same model tv and his apps work just fine.
Anyone has similar experience with these apps. Any suggestions to resolve this?