Hi guys. I have been having the same problem since I updated to Lion yesterday. Luckily, from reading all of the posts (mostly complaining), I started doing a little more searching, and it appears that Aaron Thorne is pretty knowledgeable and has come up with the solution. His terminal command sequence worked like a champ for me, and I'm back in business.
Quote from Aaron:
"
If you are lucky enough to be using OS X Lion Developer Preview and you have a NAS drive, you will most likely come across a problem trying to connect to it.
Ok the issue is that i tried to access my Buffalo LinkStation over AFP with OS X LION Beta 1 and got a error message like this one above. I couldn’t login with a registered user on my Buffalo LinkStation. The guest account worked fine but no chance with a registered one.
So i found a solution and explanation at the Apple Developer Forum. Apple disables support for the “DHCAST128? in OS X 10.7 LION , which is commonly used by NAS boxes. Apple thinks is it insufficiently secure. So all the Vendors must work with Apple for Lion compatibility.
To turn on “DHCAST128? support please do the following: "
The rest can be seen here...
http://blog.digidex.co.uk/2011/06/18/os-x-lion-connection-error-with-afp-and-workaround/?
I am using a Buffalo Linkstations LS-WTGL/R1-V3 F/W 3.09
I suggest that you cut and paste the commands rather than type them. Also, make sure you reboot each time he tells you to.
Happy Buffalo NAS fixing with NO FIRMWARE UPGRADE REQUIRED!!!!!!