Lag problems with Samsung C8000 and WiFi Netgear DGND3300

Hello,
I am using Serviio in combination with my Samsung UE40C8000 via WiFi with Netgear DGND3300 (Dual band N).
The problem is that when I want to watch a movie on my TV (only 3d and 1080p), accessing it thru the shared folder, it's real slow in loading.
The movie starts and after 5 seconds it stops and starts loading. After 10 seconds of loading the movie continues for 5 seconds and it start loading again.

Configuring my router:
ACTIVE - WMM Support Wi-Fi Multimedia (WMM)
TCP port 8895 and UDP 1900 are open in my firewall
QoS active for PORT TCP port 8895 and UDP 1900.

If the movie is 720p the quality is perfect, but if the movie is 3d SBS or 1080p there are lag.

Does anyone have any ideas or advice what I can try and do to watch movies normally, without lagging?

Regards & Thanks in advance!
Umberto

[zip]

wired connection I'm affraid

Ok,
I will try to use a cabled network.

There are bandwidth limits using WiFi?

Thanks a lot.

Regards,
Umberto

[zip]

There are bandwidth limits using WiFi?

Yes.