I can't overwrite a file on a windows share which is hidden even though I got access rights to the file. Removing hidden attribute resolves the problem.
1) Create smb.txt file on Winbox C:\
2) Connect to winbox from Linux with smbclient
3) get smb.txt works
4) put smb.txt produces -> NT_STATUS_ACCESS_DENIED opening remote file \smb.txt
5) Remove hidden attribute and I can put the file.
Just checked: This is not a bug on our side, at least not a major one. This is just how Windows behaves, there's nothing we can do about it. XP as a client and W2k3 as a Server exhibits the same behaviour. It's only that XP provides a fallback and sets the attribute to non-hidden after it has received the NT_STATUS_ACCESS_DENIED.
Downgrading the bug to "feature enhancement".