Problem: Network folders show up in the dock as a question mark and can't be opened.
Solution: Create a file nsmb.conf with the following two lines:
Save it to the desktop. Open Terminal.
Run the command "sudo bash"
Enter your sudo password. If you don't know it, look HERE.
Enter the command "cp ~/desktop/nsmb.conf /etc/nsmb.conf"
Run the command "exit" and then exit the Terminal.
The folder should show up properly now.
This forces SMB back to version 1 of the protocol for all users.