The http://checkstyle.sourceforge.net/config.html#Packages list packages are out of date with respect to the file in the jar:
I was having a problem where the error:
Embedded error: Failed during checkstyle configuration
Unable to instantiate HeaderCheck
because the Header package was not included, but instead of thinking my package definitions was wrong I was thinking I was having classpath loading difficulties.
You may also want to put a reminder in the documentation to check the file contained in the jar for the most up to date information.