I thought I resolved my beginner's issues with NFS mounting, but problems emerged.
I have fun_plug installed on DNS-313 which enables NFS on this little NAS, which auto created exports file for my storage partition on NAS (which is NTFS...looking for a method if it can be converted to Ext2).
I mounted NFS share from wdtvlive (running custom fw) as readonly. It's working great, playing smoothly even highest bitrates.
I also mounted the same NFS share from Mint 12 with rw option, added the appropriate line to /etc/fstab. This is also working as expected, read, write, speed...
But since yesterday from Mint I'm getting input output errors on copying or creating emtpy files (although I can create folder). Through NAS web interface when I run scan disk I can see NTFS inconsistency errors, when I try to repair them web page returns no feedback after 30 seconds and the scan disc button returns same errors again. When trying to write from Mint to NAS using SMB network share I'm getting the same error. At the same time wdtvlive still reads NFS mounted files from NAS perfectly.
I also tried to copy from windows to NAS mapped as a network drive, no problems at all, no errors, everything is playable afterwards.
Now... I know this is more NAS topic than Mint topic, but I need some advice if I did something wrong in NFS mounting from 2 different machines, maybe fstab line should be different from Mint?
My conclusion is that knowing that NTFS writing is buggy from every Linux, some NTFS errors emerged on the storage drive and Mint sees them since it's NFS mounted and denies to write to it, Windows doesn't see them and the NAS lets him since the errors aren't critical.
As a temporary solution I'm thinking of running fsck from the NAS itself (since I can telnet to it) or repair it from windows scan disk when I connect the enclosure to it by usb (since NAS has also usb port).
As a permanent solution I'm looking for a way to convert my storage partition from NTFS to Ext2.