From Wikipedia:
Vergil's name in English:
In the Middle Ages Vergilius was frequently spelled Virgilius. There are two explanations commonly given for this alteration. One educes a false etymology associated with the word virgo ("maiden" in Latin) due to Virgil's excessively "maiden"-like (parthenias or παÏθηνιας in Greek) modesty. Alternatively, some argue that Vergilius was altered to Virgilius by analogy with the Latin virga ("wand") due to the magical or prophetic powers attributed to Virgil in the Middle Ages. In an attempt to reconcile his non-Christian background with the high regard in which medieval scholars held him, it was posited that some of his works metaphorically foretold the coming of Christ, hence making him a prophet of sorts. This view is defended by some scholars today, namely Richard F. Thomas of Harvard.
In Norman schools (following the French practice), the habit was to anglicize Latin names by dropping their Latin endings, hence Virgil.
In the 19th century, some German-trained classicists in the United States suggested modification to Vergil, as it is closer to his original name, and is also the traditional German spelling. Modern usage permits both, though the Oxford guide to style recommends Vergilius to avoid confusion with the 8th-century Irish grammarian Virgilius Maro Grammaticus.
Some post-Renaissance writers liked to affect the sobriquet "The Swan of Mantua".
http://en.wikipedia.org/wiki/Virgil#Vir ... in_English
So the disparity isn't a feature of Latin so much as a result of the Vergil fan-club.
Edit: Oh, and while I always encourage all forms of Latinate enthusiasm, if you are addressing more than one person, the greeting is "salve
te!" So, salvete omnes! Ac salve et salvus semper sis, care Scribone!