Please look at http://safeweb.norton.com/report/show?url=gob.ar
"gob.ar" is a top-level demain for all government websites in Argentina. They, like other Spanish-speaking countries, use "gob" instead or in addition to "gov", because "gobierno" is the spanish word for "government". This broad blocking rule would be equivalent to block ".gov" in the US, so please fix it ASAP. I know NIS is mostly for US and English-speaking users, but many of us in the US also have to access websites in other countries for different reasons and I find it very annoying to be unable to do it from any of my 3 computers, which I have kept protected with NIS for 5+ years...
For the two threats identified in the report for "gob.ar" you should be blocking "sanmartiniano.gob.ar" and "municipioaranguren.gob.ar", i.e. the actual domains, instead of the whole top-level domain.