Try to open a Terminal and type findsmb
That should look up the name of the Zaurus in the SMB namespace. Usually it is "zaurus".
Then, you should try to connect smb://zaurus in Finder's Open/Server dialog.
User name seems to be ignored and password can be left open (or might be the Zaurus root password). The error message seems to have to do something with the access rights.
Hope this helps,
hns