Hello,
I am assuming the OS 9 computer is the host, and you are using OS X to connect to it. You should not need to turn on file sharing "both directions". Treat one as a Server, and the other as a Client.
On the OS 9 Mac:
* Did you go to the Appletalk control panel, and tell it to use the Ethernet port? Usually, it defaults to the printer port.
* Did you give the Mac a name in the Filesharing Control panel?
* Did you enable the particular Drive for file sharing? Do a Get Info on the hard drive or the folder that you want to share, and make sure that it is enabled.
On the OS X Mac
* Are you typing in an IP number, or using an Appletalk protocol connect?
If I had to put money on where the problem is, I bet in the Appletalk control panel, it is on the printer port.
Christian