I have discovered that the Buffalo TeraStation has a few limitations. It will not store the following types of files:
(1) Files that have a plus (‘+’) in their name. This is documented and acceptable.
(2) File paths > 120 characters in length (either this seems to be selectively enforced or I don’t understand what parts have to be (3) Folders containing an excess of 500,000 files. This isn’t really documented and I didn’t even realize I had such a crazy folder on my laptop (it was a mirror of a cgi-based website). It has been archived and deleted.
I have also discovered that connecting from OS X is much more reliable when treated as a Windows share (smb://) rather than an Apple share (afp://). I can guess that this is because the box is Linux based and Samba is pretty mature at this point compared to AppleShare stuff.
My solution to all of this? Mount the drive as smb, use Disk Utility to create a writable sparse disk image, then copy files to that. That gets past all of the filename, length, and count restrictions and allows random access to files (as opposed to a big zip or tarball.)