As of version 10.5.1, you may be able to connect to an SMB network drive, but you may not be able to browse the contents of any shared folders on the drive. Here's how you can force Finder to display the folder contents.

Connect to your network drive using the normal methods -- either Command-K or the Connect to Server option on the Go Menu. Once Finder has connected to the drive, open Terminal and type the following command:

sudo smbclient -L NETWORK_DRIVE_NAME

Replace NETWORK_DRIVE_NAME with the Windows name for your network drive. Next restart the Finder by typing sudo killall Finder. Wait for Finder to restart -- this should only take a moment -- and then run the above command again.

Open a Finder window, and click the name/IP address of your network drive. You should now be able to browse the contents of your drive.

[robg adds: I can't confirm either the problem or the solution.]