[PROBLEM] Can not mount smb share

[Armand]

This is my first post on this forum, so i don't know if it's in the right place.
I'm trying to mount a samba share in order to get NZBget to put the downloaded files on my nas.
I've installed samba and it is running, but wether i try to mount it manually or with fstab i get a "mount error(5) : Input/Output error.
The fstab entry looks like this :
//192.168.0.56/downloads /mnt/downloads cifs credentials=/home/xbian/nas,_netdev,rw,iocharset=utf8,nounix,file_mode=0777,dir_mode=0777 0 0

In the credentials file (now for testing not hidden) i've put these 2 lines :
username=username
password=password

I need to mount with cifs, because my NAS doesn't support NFS.
I'm using Xbian 1.0 Beta 1.

Can anyone help me with this ?