Just a note in case anyone else runs into this problem.
If you want to connect to a share on a Buffalo Terastation (which seems to be using Samba) from a Windows Vista installation, you need to do the following:

  • Run the Local Security Policy app – secpol.msc
  • Go to Local Policies | Security Options and choose the “Network Security: LAN Manager Authentican Level” item
  • Set it to “Send LM & NLTM, use NTMLv2 session if negotiated”

And that should sort you out.
For those of us unlucky enough to be running Vista Home (which doesn’t come with secpol), you can do the following (thanks to Patrick in the comments for this)

  • Run regedit (Windows-R, ‘regedit’) to open the registry editor
  • Find key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\
  • Change the value for the option “LMCompatibilityLevel” from 3 to 1.

Now you should be able to access the TeraStation (you may need to reboot)

[Update 25th August 2009]. A couple of commenters have been kind enough to say that this also works in Windows 7 RC and thus in Windows 7 RTM (pretty safe assumption). For what it’s worth, I have a Windows 7 RC virtual machine running and I’ve been able to connect fine without needing to make any changes that I can remember.