I am also a big fan of Julian Norwich,she was a great girl! It is interesting that Mel Gibson’s movie(The passion of the Christ) based on St. Emmericks visions, seemed to gain such prominence in our time. It seems to me God had a hand in that movie, He might also be bringing Emmericks visions to the fore front. I am not saying these visions are required for Catholics to believe in. Of Course not! I too am skeptical. However, it does seem very possible with the rantings of these Muslim Clerics, who claim they will invade Rome, and prophecy’s stating that it will happen. It bears some thought. These are not the only prophecy’s regarding the Muslims, many other saints were shown simile visions. I think at the time Pope John Paul II could of been the pontiff which the prophecy relates to, but you are correct it was just an interpretive opinion. I am not familiar with doctrinal messages that St. Cathrine of Siena had in visions that turned out to be in error, so I can not comment to that, but would like to know what they were. As far as St. Malachi, he had it right, he said the pope would be the glory of the olives, He came from a Benedictine order,and that is in fact their motto. He of course took on the name Pope Benedict as it turned out a perfect fit. In fact, people in Ireland who make bets on Inter-trade cleaned up because of the prophecy from Malachi.
Nevertheless, we are well-advised to take a skeptical view of visions and so forth: all the genuine visionaries certainly did! Most of them didn't publish or publicize their visions unless ordered to do so by their confessor or religious superior. For a bit about St Catherine of Siena's erroneous vision, you can see here (about 1/3 of the way down the page) --- altogether, this whole article has a good discussion on reasons to be cautious about "messages."
Concerning St. Malachi: wrong on two counts. (1) Pope Benedict is not a member of the Benedictine order, and (2) "the glory of the olives" is not one of the four Benedictine mottoes. They are "Ora et Labora" (Work and Pray), "Pax" (Peace), "Ut in omnibus glorificetur Deus" (That in all things God may be glorified), and "Let nothing else be preferred to the Work of God."
There is one small congregation within the Benedictine Order, in rural Italy, called the "Olivetians" but it has no particular link to Pope Benedict; and besides, their motto is not "the glory of the olives."
Moreover, Pope Benedict didn't say he chose his name because of St. Benedict of Nursia, but rather in honor of Pope Benedict XV, who was pope during World War I and a strong advocate for ending the war.
So, sorry, it really doesn't pan out. Not unless you treat the prophecy like one of my old sweaters, which I sometimes stretch way too far, to cover way too much! :o)