[cem] Error when using cem with >2 treatments

I'm trying to use cem to do matching involving 3 treatments. Prof. King (http://comments.gmane.org/gmane.comp.lang.r.matchit/393) indicated that this can be done. When I tried it, I got an error message - imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error There was a discussion on this site on July 24 of 2013 about a similar issue. In that case, there were only 2 treatments but a treatment of ".", along with "1" and "2", showed up in the summary table. The suggestion was to add "if indepvote != ." to the cem call." While I'm sure that there are no missing values of my treatment variable, I still tried to add the if clause to my cem call. But it didn't help. I got another error: . cem margins1 age, tr(approach1) if approach1 != . option if not allowed r(198); Any ideas of how I can proceed? Thanks. Dennis Hanseman