I decided to make the topic the error message, since it’s what people often are searching for when experiencing a problem :-).
Problem scenario: You’ve downloaded a file from t3h intranetz on your Snow Leopard MacBook, and opens the file (possibly a PDF or DMG file) using the Mac. Then you try to copy the file to your SMB/CIFS network share (Samba/Synology/QNap/ReadyNAS/{your NAS device here}), but get the following dreaded and dumbfounding error message:
The operation can’t be completed because you don’t have permission to access some of the items.
Several times this nasty bug has bitten me, and I assume I’m not the only one :-).