If you create a matrix variable that contains a / (I didn't test other characters) It will create the wrong directory structure causing hudson to create wrong URLs as well as misbehave in the filesystem.

This seems like an oversight in the escaping sequence for those variables.

The correct behavior will be to either replace the directory names with another valid character (say a dash) or escape them in both the filesystem and the URLs and then decode them back to be available as values in the Build script.

More info and a workaround in the original mailing list post http://groups.google.com/group/hudson-users/browse_thread/thread/4a9f54d146189c15/