Could we get java.lang.NoClassDefFoundError due network issues - ajax

Question

I am running a client server web-application, and am trying to navigate to a tab after loading a page. On clicking the history tab, the browser shows "Internal Error". The server logs shows a null pointer exception, caused by NoClassDefError....
The issue is only reproducible when I connect through VPN from home(slow connection to the server) , and it does not occur when I am connecting from Lan (faster connectivity to the server)
The exception trace is shown below. Could someone help to debug this issue? The source code does not provide much details, and this issue seem to be related to the network?
Trace:
2015-05-08 13:27:28,452 ERROR [qtp1582565014-105] [l.ngna.platform.wicket.AbstractApplication] unexpected error
org.apache.wicket.WicketRuntimeException: Method onLinkClicked of interface org.apache.wicket.markup.html.link.ILinkListener targeted at [IndicatingAjaxFallbackLink [Component id = link]] on component [IndicatingAjaxFallbackLink [Component id = link]] threw an exception
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:268)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:216)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:240)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:226)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:861)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
at l.ngna.platform.wicket.NaWicketFilter.processRequestCycle(NaWicketFilter.java:41)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:230)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at l.ngna.platform.usermgmt.security.NaSpnegoAuthenticationFilter.doFilter(NaSpnegoAuthenticationFilter.java:51)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at l.ni.preauthentication.NiPreAuthenticationFilter.doFilter(NiPreAuthenticationFilter.java:45)
at l.ngna.platform.usermgmt.NaPreAuthenticationFilter.doFilter(NaPreAuthenticationFilter.java:33)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:85)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.springframework.web.multipart.support.MultipartFilter.doFilterInternal(MultipartFilter.java:119)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1423)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:450)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:138)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:564)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:213)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1083)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:379)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:175)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1017)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:136)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:109)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:445)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:260)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:225)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.run(AbstractConnection.java:358)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:596)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:527)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
... 51 more
Caused by: java.lang.NoClassDefFoundError: Could not initialize class l.ngna.optical.gui.network.tree.contour.ContourChartPanel
at l.ngna.optical.gui.network.tree.contour.ContourPanel.<init>(ContourPanel.java:61)
at l.ngna.optical.gui.network.page.PassiveOpticalNetworkViewPage$4.getPanel(PassiveOpticalNetworkViewPage.java:352)
at l.ngna.optical.gui.network.page.PassiveOpticalNetworkViewPage$4.getPanel(PassiveOpticalNetworkViewPage.java:350)
at org.apache.wicket.extensions.markup.html.tabs.TabbedPanel.setCurrentTab(TabbedPanel.java:414)
at org.apache.wicket.extensions.markup.html.tabs.TabbedPanel.setSelectedTab(TabbedPanel.java:389)
at l.ngna.platform.wicket.ajax.IndicatingAjaxTabbedPanel$1.onClick(IndicatingAjaxTabbedPanel.java:27)
at org.apache.wicket.ajax.markup.html.AjaxFallbackLink.onClick(AjaxFallbackLink.java:148)
at org.apache.wicket.markup.html.link.Link.onLinkClicked(Link.java:190)
... 56 more