Any ideas why only one of my mailbox servers is unable to access the admin console? I get this in my web browser:

Code:
Internal Server Error

The server has encountered an internal error.
And this is from /opt/zimbra/log/zmmailboxd.out:

Code:
2012-11-28 10:55:27.594:WARN:oejs.ServletHandler:/zimbraAdmin/
org.apache.jasper.JasperException: PWC6345: There is an error in invoking javac.  A full JDK (not just JRE) is required
        at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:124)
        at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:296)
        at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:372)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:433)
        at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:608)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:476)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:366)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
        at com.zimbra.webClient.servlet.JspServlet.service(JspServlet.java:56)
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:565)
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:479)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:542)
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:227)
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1031)
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:406)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:186)
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:965)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
        at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:288)
        at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:115)
        at org.eclipse.jetty.servlet.DefaultServlet.doGet(DefaultServlet.java:557)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:565)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1361)
        at com.zimbra.webClient.filters.ForwardFilter.doFilter(ForwardFilter.java:61)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1332)
        at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(SetHeaderFilter.java:57)
        at com.zimbra.webClient.filters.SetHeaderFilter.doFilter(SetHeaderFilter.java:246)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1332)
        at org.eclipse.jetty.servlets.UserAgentFilter.doFilter(UserAgentFilter.java:77)
        at org.eclipse.jetty.servlets.GzipFilter.doFilter(GzipFilter.java:181)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1332)
        at org.eclipse.jetty.servlets.DoSFilter.doFilterChain(DoSFilter.java:464)
        at org.eclipse.jetty.servlets.DoSFilter.doFilter(DoSFilter.java:327)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1332)
        at com.zimbra.webClient.filters.CharEncodingFilter.doFilter(CharEncodingFilter.java:35)
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1332)
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:477)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:227)
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1031)
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:406)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:186)
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:965)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
        at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:250)
        at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:149)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
        at org.eclipse.jetty.rewrite.handler.RewriteHandler.handle(RewriteHandler.java:312)
        at org.eclipse.jetty.server.handler.DebugHandler.handle(DebugHandler.java:77)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
        at org.eclipse.jetty.server.Server.handle(Server.java:349)
        at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:452)
        at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:884)
        at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:938)
        at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:634)
        at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:230)
        at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:77)
        at org.eclipse.jetty.io.nio.SslConnection.handle(SslConnection.java:191)
        at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:606)
        at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:46)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:603)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:538)
        at java.lang.Thread.run(Thread.java:722)
I compared it to the other mailbox server that can access the admin console, and the file permissions look the same. The $PATH variable is the same. What am I missing?