I am getting the following error when trying to create tasks, any ideas on what I need to do to fix?

2008-02-29 10:12:28,304 WARN [btpool0-0] [name=user@mydomain.com;mid=5;ip=10.0.1.60;ua=Zimbr aWebClient - FF2.0 (Win)/5.0.2_GA_1975.RHEL5;] SoapEngine - handler exception
java.lang.NullPointerException
at com.zimbra.cs.mailbox.CalendarItem.reindex(Calenda rItem.java:186)
at com.zimbra.cs.mailbox.Mailbox.endTransaction(Mailb ox.java:5716)
at com.zimbra.cs.mailbox.Mailbox.addInvite(Mailbox.ja va:3542)
at com.zimbra.cs.mailbox.Mailbox.addInvite(Mailbox.ja va:3474)
at com.zimbra.cs.service.mail.CalendarRequest.sendCal endarMessageInternal(CalendarRequest.java:342)
at com.zimbra.cs.service.mail.CalendarRequest.sendCal endarMessage(CalendarRequest.java:196)
at com.zimbra.cs.service.mail.CreateCalendarItem.hand le(CreateCalendarItem.java:78)
at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEng ine.java:342)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:208)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:113)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.jav a:272)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:727)
at com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:174)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1093)
at org.mortbay.servlet.UserAgentFilter.doFilter(UserA gentFilter.java:81)
at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter .java:132)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1084)
at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:360)
at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:716)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:406)
at org.mortbay.jetty.handler.ContextHandlerCollection .handle(ContextHandlerCollection.java:211)
at org.mortbay.jetty.handler.HandlerCollection.handle (HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:139)
at org.mortbay.jetty.handler.RewriteHandler.handle(Re writeHandler.java:176)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:139)
at org.mortbay.jetty.Server.handle(Server.java:313)
at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:506)
at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:844)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:644)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:205)
at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:381)
at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:396)
at org.mortbay.thread.BoundedThreadPool$PoolThread.ru n(BoundedThreadPool.java:442)