You seem to be using a custom DITA Open Toolkit installation so I'm not sure what changes you made to it.
Did you copy it from an Oxygen installation? If so, from what Oxygen version did you copy it?
Basically an Eclipse Help transformation must be applied on a DITA Map. Is the cos_Admin_Guide.xml
file a DITA Map or a topic?
If it is a topic, please try to apply the publishing on a DITA Map which refers to the topic.
If it's a DITA Map maybe you should try renaming it with the ditamap
extension, the DITA Open Toolkit might have problems with this.
Also the DITA Open Toolkit has always had problems when a DITA Map references resources which are outside of the folder where the map is located. So this might be another possibility of why this fails for you:
http://www.oxygenxml.com/doc/ug-oxygen/ ... -refs.html