Just installed Hudson for the first time (using WebStart). When doing any kind
of submit to 'configSubmit' I get the exception below:

Status Code: 500
Exception:
Stacktrace:

net.sf.json.JSONException: A JSONObject text must begin with '{' at character 0 of
at net.sf.json.util.JSONTokener.syntaxError(JSONTokener.java:512)
at net.sf.json.JSONObject._fromJSONTokener(JSONObject.java:881)
at net.sf.json.JSONObject._fromString(JSONObject.java:1102)
at net.sf.json.JSONObject.fromObject(JSONObject.java:175)
at net.sf.json.JSONObject.fromObject(JSONObject.java:145)
at hudson.StructuredForm.get(StructuredForm.java:16)
at hudson.model.Job.doConfigSubmit(Job.java:698)
at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:277)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:103)
at org.kohsuke.stapler.Function.bindAndinvoke(Function.java:59)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:63)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:294)
at org.kohsuke.stapler.MetaClass$9.doDispatch(MetaClass.java:240)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:294)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:231)
at org.kohsuke.stapler.Stapler.service(Stapler.java:79)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:71)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Unknown Source)