Remove (or better rename) the default.conf mentioned in the error message.
It seems to be broken. If you have a default.conf.cbTemp in the same folder, you can try to rename it by removing the .cbTemp (after renaming the original file).
If it exists it can work or not, if it does not exist or is corrupted remove any default.conf (it will be created from scratch).
You have to setup C::B again after deleting it.