Hi all,
Just to let you know, Apple has released 10.6.7.. They specifically mention on the release pages ( http://support.apple.com/kb/HT4472 )
"Resolve an issue when transferring files to certain SMB servers."
After applying the update, I found SMB to be more reliable (well, it worked!) on the DNS-320 whereas previously I had many issues...
I'd be interested to hear other experiences.