ant install problem

I'm using ant to install applications during development as recommended by http://jakarta.apache.org/tomcat/tomcat-5.0-doc/appdev/processes.html
This used to work well on tomcat4, but now the application doesn't start.
It gets visible in the tomcat manager, but is not started. When I press start to make it run, the manager says "FAIL - Application at context path /go could not be started" and my verbose logging gives me

Exception during cleanup after start failed
LifecycleException:  Container StandardContext[/go] has not been started
        at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4466)
        at org.apache.catalina.core.StandardContext.start(StandardContext.java:4371)
        at org.apache.catalina.core.StandardHostDeployer.start(StandardHostDeployer.java:830)
        at org.apache.catalina.core.StandardHost.start(StandardHost.java:991)
        at org.apache.catalina.manager.ManagerServlet.start(ManagerServlet.java:1322)
        at org.apache.catalina.manager.HTMLManagerServlet.start(HTMLManagerServlet.java:530)
        at org.apache.catalina.manager.HTMLManagerServlet.doGet(HTMLManagerServlet.java:104)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
        at java.lang.Thread.run(Thread.java:534)

The application I try to install is stripped down to the simplest possible, only a jsp.

I've been looking hard for a solution (and the cause), but cannot find any info. Can someone out there give me a clue?

... and it all works well if I and deploy the .war with tomcat manager...

I'm using gentoo linux and tomcat 5.0.27-r4
Anyone seen this?