If you are trying to share a printer in Windows 7 and get the error 0x000006d9, check your system services. If your Windows Firewall service is off, turn it on and try again.
Worked for me when I tried to share a printer. I guess W7 was trying to add a rule to allow the printer to be accessible but as the service was off, it couldn't modify it and hence couldn't share it out.
