Is it possible to setup a remote server to store a folder with encrypted contents, which is impossible to read by the server, but is editable by multiple clients?
It seems like duplicity is a tool for this, but I'm not sure if any data loss is possible if 2 workstations try to edit the same file simultaneously?
I think that ownCloud will probably do what you're looking for.
If you can't/don't want to run ownCloud, and want to roll your own solution, you'll need:
(1) a capable revision control system to deal with conflicts, like git, hg or bzr;
(2) encryption tools like TrueCrypt, eCryptFS or Duplicity;
(3) a method of accessing the file server, such as FTP or SSH; and
(4) a number of complex hand-crafted shell scripts to tie the whole thing together.