Found it here. http://confluence.public.thoughtworks.org/display/CCNET/Xml+Log+Publisher
The Xml log publisher is used to create log files used by the CruiseControl.NET control panel, so if you do not define a section, the control panel will not work correctly. You should put in the section, after any file merging tasks, in your project configuration block. Examples
Minimalist example:
<xmllogger />
Full example:
<xmllogger logDir="c:\myproject\buildlogs" />