Pressing the "Test Connection" button needs several minutes to say that the connection was successful. Also connecting at runtime needs very, very long time. Feels like some kind of incompatibility with W2K8R2 DC / W2K8R2 Share.
The same share and DC work fast and nearly instantly reacting when using SMBFS on the Debian-driven master; it's really only the CIFS plugin which is so slow.
Would be great if this could be fixed. I am willing to provide more information and do some tests, once I am exactly told what to do.