the problem can be solved if you allow the permssion of parental folder of your share points to have at least Read Only permission for User and Group:
Group: Read Only
Others: Read Only (or No Access)
In my case, it is strange that PCs can still do the search to the Snow Leopard Server by SMB protocol while Mac using AFP cannot even when the parental folder had permission 600. This could be a secure issue in Snow Leopard's SMB1.0 protocol. Note that SMB in Snow Leopard is SMB1.0, which is less secure and hence deprecated after Snow Leopard. From Lion onwards, all OS X uses SMB2.0 and/or SMB X.
Oh, yes, there is one more thing:
you may find your scanner using SMB protocol stopped functioning properly if you use (Mountain) Lion client and (Mountain) Lion server. It boils down to Apple's silent change of SMB protocol from SMB1.0 to SMB2.0. Solution? Use FTP protocol for now. Don't blame Apple too much because Apple had to follow the rules of GPLv3. The SMB issue will go on as Microsoft introduces its own SMB 3.0 protocol in Windows 8 while Apple introduces its SMB verison dubbed SMB X.
Hope this helps.