This is resolved, I switched in the 4.2.1 jars and also corrected a mismatch between the compile and runtime JDKs, for some reason the system was overriding my JAVA_HOME setting (6.1) and running the client with a 5.0 JVM. I did not have to use setParser.
I did try running the 'new' 4.2.1 SolrJ client against SOLR 3.6 and got this error in the server log: 2013-05-07 16:14:34,835 WARN [org.apache.solr.handler.XmlUpdateRequestHandler] (http-0.0.0.0-18841-Processor15) Unknown attribute doc/field/@update so I've settled for separate 3.6 and 4.2.1 versions. Your info helped a lot, thanks Shawn. DK -- View this message in context: http://lucene.472066.n3.nabble.com/ConcurrentUpdateSolrServer-Missing-ContentType-error-on-SOLR-4-2-1-tp4061160p4061416.html Sent from the Solr - User mailing list archive at Nabble.com.