in file /etc/isdn/isdn.conf there should be no country code by default. isdn configuration utilties cannot change this country code, so isdn configuration works only in one country (I guess the default is Germany). if there wasn't any country code by default, it would work.
i have read the isdn4k-utils documents again. It says the COUNTRYCODE must be set, otherwise isdnlog does not work. howerver the next isdn-config-0.19 will do it for you.