cant write to ntfs hdd

[swinxx]

hello folks.

i have configured my ntfs hdd to work with my rasp xbian as media hdd. works great.
then i have configured my mac to connect the the hdd via network connection. works.
xbmc on my mac found the nfs folder and i can stream videos and stuff from my rasp to my mac.

BUT!! when i try to write a movie from the mac to the Rasp HDD i get some strange error messages..
first i must enter my mac user name and password,
then it the finder tells me that the file already exists and asks me if i want to overwrite it??
and then i got the message that it can not write because a file already exitst..
when i check that there is indeed a file there, but with 0kb..

can anyone help please, cause i am a newbie and have no idea what i have done wrong.

thx swinxx.