smbclient works but mount_smbfs fails

I am running across a rather strange issue with a Zonet NAS I recently purchased. The device shares files via FTP and SMB over the network. I have an iMac running Lion and a Macbook Pro running Snow Leopard. I can connect just fine from the iMac but not from the Macbook Pro using the Go -> Connect to Server menu in Finder.

From the Macbook I always receive an authentication error regardless of the account I use. From the iMac the exact same parameters work fine.

I tried some commandline utilities from the Macbook Pro. smbclient works fine. So the command:

smbclient //10.0.0.50/photoshare -U alext

works fine, it prompts me for the password and gives me a command line session where I can transfer files.

However the command:

mount_smbfs //alext@10.0.0.50/photoshare /Volumes/photoshare

always returns the error:

mount_smbfs: server rejected the connection: Authentication error

This is very puzzling. There must be something strange with my SMB client on the Macbook but I have no idea what is going on. Any ideas would be appreciated.