I'd say the warning is a good idea, and you can add a blurb about people having to use the smbpasswd command to actually add people to the smb database, as the Buffalo WWW interface only adds the user entries to the smb.conf file, users created before upgrading samba are fine.
However this error doesn't happen on an orginial TeraStation 1... that's the weird part.
PS. Don't remove the software
I find it very usefull!
PSS. I was able to build the latest Samba 3.5.6 code branch on my TeraStation Pro 1 however I couldn't get it to run...