I have a DNS-320 purchased in the UK; came with 2.02 firmware - which I believe may suffer from both of the reported (and IMO extremely serious) data integrity issues:
(a) (Large?) Files copied to NAS from CIFS client can end up showing with zero-length
(b) Corruption when files are modified (especially with Outlook .PST files?)
I can't "roll back" to the older version 2.00 as my NAS came already loaded with the newer firmware, so at present I'm stuck with a NAS that I daren't use for any important/valuable data in case either of the two bugs were to bite and that data was trashed

But I did read about that unofficial 2.03b03 firmware that is reported to fix at least the "0kb" problem - so I am hoping that there will be an official fix forthcoming (or at minimum an official beta)
FYI I went hunting and did find the link to that unofficial beta on a cached web page - but won't be trying it simply because it is of unknown pedigree...
(a) There's no release note in the ZIP-archive or hint in the firmware file name as to where it came from or what hardware/countries it applies to (the firmware file name is "DLINK_DNS320.2.03b03(2.13.0618.2012)(BETA)", having a "modified" date/time of 18 June 2012, 15:47:20).
(b) The IP address of the FTP-server from where it came is allocated to an ISP in Sweden
Regards,
Richard