A few people have noticed a problem in Snow Leopard where depending on the view being used, the Finder may not properly manage files on shared SMB resources. Specifically, when in column view in the Finder, while files and folders can be created and deleted, folders cannot be renamed. In some instances doing this leads to the Finder crashing and relaunching but for the most part folders just will not rename.
In my testing, the OS X Windows file sharing works just fine when connecting to a variety of Windows PCs running anything from Windows 98 through Windows Vista; however these PCs are running Microsoft's SMB/CIFS networking technology and are not using the Samba suite.
This problem seems to revolve around a Samba version incompatibility between OS X's implementation and newer versions of Samba running on Linux and Unix machines. Several users have reported the problem seems to happen when they connect to their servers running Samba 3.3.x, whereas other servers that are running prior versions seem to function just fine.
Since this problem seems to only happen in one Finder view mode, it's clearly a problem in OS X but could potentially be helped by setting up the share again on the server and ensuring ACLs for the share and enclosing folders are set up to give the proper permissions.
For the most part it's a minor bug that will hopefully be addressed with a Samba update either for the servers or for the OS X client; however, in the mean time if you are experiencing this bug you should be able to rename folders by first switching to another Finder view.