What 82ross has said regarding the config.xml file is basically correct, however we may from time to time include a tag that MUST be present.
A bug in the 10/13 CVS update for instance means that the <autolaunchvideo> tag must be present in order for it to load correctly.
This bug was corrected in an update to the CVS repository on 10/15.
Note also, that deleting the system.bin file, while prudent, is NOT necessary. XBMP has had version checking in this file for at least the last 2 months, so you'll only have problems if someone changes the format without updating the version number, which is not all that likely. Even if they do, the worst that will happen is that some of the settings will be stuffed up. It should at least boot up correctly.