Transfer large file to Buffalo NAS failed (10 Gb+)

[deciBel]

I have trouble transfering large files (10+ Gb) from my PC to the server. The file transfer seems to be cut down to aprox 1 Gb, when transfer is complete.
The file I am trying to copy over, is a .mkv file. I have tested the file locally on my PC so I am sure the file works fine. I have also tried to transfer another movie - and got the same error.

I have also tried to zip it, then copy it over to the NAS, then unzip it. But it doesnt help.

 

I have plenty of space avaliable on my server ( aprox. 2TB). The server is used as a media server, and I have 120 movies stored in my "movies" folder that I am trying to copy my new .mkv file into.   The server and my network has been working fine for at least 3 months now, until last week when I discovered this error...

 

-Are there any limitation on how many Gb a folder can be on a Buffalo NAS server ?