I am getting strange problem with my jboss3.0.4. It is not compiling jsp file . Giving exception:

java.lang.NullPointerException
at org.apache.tools.ant.util.FileUtils.resolveFile(FileUtils.java:330)
at org.apache.tools.ant.Project.resolveFile(Project.java:618)
at org.apache.tools.ant.types.Path.resolveFile(Path.java:451)
at org.apache.tools.ant.types.Path.translatePath(Path.java:353)
at org.apache.tools.ant.types.Path$PathElement.setPath(Path.java:119)
at org.apache.tools.ant.types.Path.setPath(Path.java:167)
at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:262)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:324)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:474)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:184)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:289)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:240)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:260)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2396)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:469)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1040)
at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1151)
at java.lang.Thread.run(Thread.java:536)

Some time it works when i restart the server. Please help me.
Naresh