Hello,
The problem is caused by "Ignore multiple sources (Itemid)" option set to "Yes" and the specific menu configuration. If you have CB component located somewhere in menu and accessible by registered users only, after registration, it tries to redirect to that menu item, BUT you are not logged in, so you don't have access. This is avoided by NOT using Itemid variable by CB, but when Ignore multiple sources is enabled, JoomSEF treats both URLs the same.
SOLUTION: You need to set "Ignore multiple sources (Itemid)" option to "No" in JoomSEF's configuration (don't forget to delete the already created URL to CB component from JoomSEF's database and clean the cache). If disabling this feature causes duplicities, try using the "Exclude source info" and "Reappend source info" options - see documentation for more information.
Best regards,
ARTIO Support Team