aTV Flash black- problem with HDD

Hi, i have purchased aTV Flash Black.

Connected to my router i have an usb HDD.

 

Via Mac i can play the file on the network HDD without problem.

Via ATV (using Media Player and XBMC) with mkv file of large dimension i have some problem like lost connection or buffering every 30 seconds.
I have tryed using AFP and SMB with drive in NTFS or HFS+. same result!

I have tryed to install Plex on my mac, and set the Library for take files in the network HDD; i have installed Plex in my ATV and… all perfect!

In this situation the files start from the network HDD come in my mac and return in ATV without problem but i need a solution based only on ATV and Network HDD.

I have tryed to connect ATV by cable to my router, by 2.4Ghz Wifi and by 5 Ghz. 

My router is a Netgear WNDR3800. AppleTV have DHCP static lan ip, and in the DMZ.

 

Please suggest a solution! 

Thanks and sorry for my english

1.1 not resolve the problem!

The atv2 isn’t exactly the strongest piece of hardware for decoding files you have to remember. By using the plex client, you’re putting the encoding task onto your mac, which then streams to the apple tv. Best way to do it for massive HD rips.