This is the second time I have seen the error below. This time was after
upgrading Hudson (pfexec pkg install hudson). I don't remember if the last time
was also.

The solution to get it to start working was to remove the following line:
<permission>hudson.model.Item.Release:malachi</permission>

Once that was removed, Hudson started fine and I just had to re-enable "release
job" for myself.

Here's the stack trace:
[!] Error

hudson.util.IOException2: Unable to read /home/hudson/config.xml
at hudson.XmlFile.unmarshal(XmlFile.java:150)
at hudson.model.Hudson.load(Hudson.java:1975)
at hudson.model.Hudson.(Hudson.java:557)
at hudson.WebAppMain$2.run(WebAppMain.java:190)
Caused by: com.thoughtworks.xstream.converters.ConversionException: null : null
---- Debugging information ----
cause-exception : java.lang.IllegalArgumentException
cause-message : null
class : hudson.model.Hudson
required-type : hudson.security.ProjectMatrixAuthorizationStrategy
path : /hudson/authorizationStrategy/permission[6]
line number : 13
-------------------------------
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:89)
at
com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:63)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at
hudson.util.RobustReflectionConverter.unmarshallField(RobustReflectionConverter.java:262)
at
hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:222)
at
hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:173)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at
com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:63)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at
com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:923)
at hudson.util.XStream2.unmarshal(XStream2.java:65)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:909)
at hudson.XmlFile.unmarshal(XmlFile.java:146)
... 3 more
Caused by: java.lang.IllegalArgumentException
at
hudson.security.GlobalMatrixAuthorizationStrategy.add(GlobalMatrixAuthorizationStrategy.java:85)
at
hudson.security.GlobalMatrixAuthorizationStrategy.add(GlobalMatrixAuthorizationStrategy.java:99)
at
hudson.security.GlobalMatrixAuthorizationStrategy.access$200(GlobalMatrixAuthorizationStrategy.java:65)
at
hudson.security.GlobalMatrixAuthorizationStrategy$ConverterImpl.unmarshal(GlobalMatrixAuthorizationStrategy.java:215)
at
hudson.security.ProjectMatrixAuthorizationStrategy$ConverterImpl.unmarshal(ProjectMatrixAuthorizationStrategy.java:82)
at hudson.util.XStream2$AssociatedConverterImpl.unmarshal(XStream2.java:141)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
... 19 more

Hudson ver. 1.318 (private-07/31/2009 06:09-kohsuke)