I have Solr 4.6.1 on the server and just upgraded my indexer app to SolrJ 4.6.1 and indexing ceased (indexer returned "No live servers for shard" but the real root from the Solr servers is below). Note that SolrJ 4.6.1 is fine for the query side, just not adding documents.
21:35:21.508 [qtp1418442930-22296231] ERROR o.a.solr.servlet.SolrDispatchFilter - null:java.lang.RuntimeException: Unknown type 19 at org.apache.solr.common.util.JavaBinCodec.readVal(JavaBinCodec.java:232) at org.apache.solr.client.solrj.request.JavaBinUpdateRequestCodec$1.readOuterMostDocIterator(JavaBinUpdateRequestCodec.java:139) at org.apache.solr.client.solrj.request.JavaBinUpdateRequestCodec$1.readIterator(JavaBinUpdateRequestCodec.java:131) at org.apache.solr.common.util.JavaBinCodec.readVal(JavaBinCodec.java:223) at org.apache.solr.client.solrj.request.JavaBinUpdateRequestCodec$1.readNamedList(JavaBinUpdateRequestCodec.java:116) at org.apache.solr.common.util.JavaBinCodec.readVal(JavaBinCodec.java:188) at org.apache.solr.common.util.JavaBinCodec.unmarshal(JavaBinCodec.java:114) at org.apache.solr.client.solrj.request.JavaBinUpdateRequestCodec.unmarshal(JavaBinUpdateRequestCodec.java:158) at org.apache.solr.handler.loader.JavabinLoader.parseAndLoadDocs(JavabinLoader.java:99) at org.apache.solr.handler.loader.JavabinLoader.load(JavabinLoader.java:58) at org.apache.solr.handler.UpdateRequestHandler$1.load(UpdateRequestHandler.java:92) at org.apache.solr.handler.ContentStreamHandlerBase.handleRequestBody(ContentStreamHandlerBase.java:74) at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:135) at org.apache.solr.core.SolrCore.execute(SolrCore.java:1859) at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:721) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:417) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:201) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:455) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1075) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:384) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1009) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116) at org.eclipse.jetty.server.Server.handle(Server.java:368) at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489) at org.eclipse.jetty.server.BlockingHttpConnection.handleRequest(BlockingHttpConnection.java:53) at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:953) at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:1014) at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:953) at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:240) at org.eclipse.jetty.server.BlockingHttpConnection.handle(BlockingHttpConnection.java:72) at org.eclipse.jetty.server.bio.SocketConnector$ConnectorEndPoint.run(SocketConnector.java:264) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608) at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543) at java.lang.Thread.run(Thread.java:724)