I have been doing some forum reading today, and i luckily saw answers to both your questions.........
SMB has a bug currently, it will not allow top level shares, you will have to put the media in a directory for now, i think they are trying to implement a fix for the next release, and also the only way around the stacking is to use the stack/unstack button, which in XBMC is easily accessable in the my videos menu.
- Shorty <