Searches including a period (".") return HTTP Status 500 from SolR

Some searches of the form [a-z]+\.[a-z]+ return an error ("The Apache Solr search engine is not available. Please contact your site administrator.")

I noticed this when testing apachesolr_autocomplete but got the same message when that module was disabled. I also see this error when searching directly from the solr admin interface at http://HOST:8080/solr/CORE/admin/

To test this I created 100 nodes using devel_generate. Searching for "sagaciter.jugis" or "sagacit.jugi" results in an error, but a search for "sagaci.jugi" succeeds. Reproduced using Apache Solr Search Integration 6.x-1.2 and 6.x-2.0-beta3 on separate SolR cores with Tomcat 6.0.28-2ubuntu1 and solr-tomcat 1.4.0+ds1-2ubuntu1.

Error message from tomcat below:

HTTP Status 500 - org/apache/lucene/index/memory/MemoryIndex java.lang.NoClassDefFoundError: org/apache/lucene/index/memory/MemoryIndex at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.getReaderForField(WeightedSpanTermExtractor.java:361) at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extractWeightedSpanTerms(WeightedSpanTermExtractor.java:282) at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extract(WeightedSpanTermExtractor.java:230) at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extract(WeightedSpanTermExtractor.java:158) at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.getWeightedSpanTerms(WeightedSpanTermExtractor.java:414) at org.apache.lucene.search.highlight.QueryScorer.initExtractor(QueryScorer.java:216) at org.apache.lucene.search.highlight.QueryScorer.init(QueryScorer.java:184) at org.apache.lucene.search.highlight.Highlighter.getBestTextFragments(Highlighter.java:226) at org.apache.solr.highlight.DefaultSolrHighlighter.doHighlighting(DefaultSolrHighlighter.java:335) at org.apache.solr.handler.component.HighlightComponent.process(HighlightComponent.java:89) at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:195) at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:131) at org.apache.solr.core.SolrCore.execute(SolrCore.java:1317) at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:338) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:241) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:563) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:636)