That is probably an OS X issue, since Opus just asks Windows to get a directory listing and the rest is up to Windows and completely standard. (Explorer may use slightly different flags, and maybe Apple only tested things with Explorer, but there isn't much Opus could do here to make things go wrong, and you're bound to find problems in other software if you look.)
The folder with no name and a C:-drive icon at the top of the list is also indicating something is wrong in the way the OS X server is behaving.
Assuming you're using OS X Mavericks, there seem to be a lot of complaints about its SMB server, including disconnections, blank file/folder names and missing folders. Some people in the thread say forcing Windows to only use SMB v1 helped (but that will also slow down access to all network shares), and others in the same thread say they have the problem after upgrading an existing install to Mavericks but didn't have the problem on a clean install.