After upgrade from 6.x to 7.1.0, Zimbra Mobile stopped to work. I can not figure out what is wrong.

In mailbox.log I get this error message when a mobile is trying to connect:
Code:
2011-04-15 12:32:43,650 WARN  [btpool0-12://mail.domain.net/Microsoft-Server-ActiveSync?Cmd=Sync&User=myname%40domain.net&DeviceId=androidc661430843&DeviceType=Android] [] log - /service/extension/zimbrasync
com.zimbra.common.service.ServiceException: system failure: Extension HTTP handler not found at /zimbrasync
ExceptionId:btpool0-12://mail.domain.net/Microsoft-Server-ActiveSync?Cmd=Sync&User=myname%40domain.net&DeviceId=androidc661430843&DeviceType=Android:1302863563650:2b73323f0993844d
Code:service.FAILURE
	at com.zimbra.common.service.ServiceException.FAILURE(ServiceException.java:248)
	at com.zimbra.cs.extension.ExtensionDispatcherServlet.getHandler(ExtensionDispatcherServlet.java:139)
	at com.zimbra.cs.extension.ExtensionDispatcherServlet.service(ExtensionDispatcherServlet.java:92)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:814)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
	at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(SetHeaderFilter.java:79)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
	at org.mortbay.servlet.UserAgentFilter.doFilter(UserAgentFilter.java:81)
	at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter.java:155)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:218)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:422)
	at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
	at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.handler.rewrite.RewriteHandler.handle(RewriteHandler.java:230)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.handler.DebugHandler.handle(DebugHandler.java:77)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:543)
	at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:946)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
	at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:451)
Release 7.1.0_GA_3140.UBUNTU8_64 UBUNTU8_64 NETWORK edition.