Someone updated subversion to 1.5 on the dev server (Red Hat 4.3.0-8) this morning, and consequently broke my zsh tab completion.
% svn add[TAB]
_arguments:comparguments:303: invalid argument: ARG
This bug report for Ubuntu describes the same problem, and the fix works for me, except that the file to edit (replacing "/ arg/:arg:" with "/ (arg|ARG)/:arg:") is located in /usr/share/zsh/4.3.4/functions/_subversion.
Update:
If you're on a system where you don't have privileges to write to /usr/share/zsh and the system admins are too retarded (sorry, "don't have the resources") to apply a patch that changes two lines, you can override the subversion completion like this:
mkdir ~/zsh
cd ~/zsh
wget http://gvn.googlecode.com/svn/trunk/contrib/zsh/_subversion
Then include the directory in your $fpath by placing the following in your .zshrc:
fpath=(~/bin/zsh $fpath)
Of course, ~/zsh is arbitrary, put it wherever you like.