I went back and read rule 40(a) through 40(e) and could not find any support for the idea that new nominations could be made prior to a second or subsequent ballot. Rule 40 is a sequential directive with specified procedures for each step of the proceeding. Subsection (a) first outlines how the roll of states will be taken, (b) how and when demonstration of support is evidenced by candidates prior to nomination, (c) time of nomination speeches, (d) how to deal with announcement when a candidate receives a majority and how that candidate is declared the party nominee, (e) procedure to be followed if no candidate receives a majority vote on a given ballot.
It would appear that it is rule 40(e) that controls what happens when no one receives a majority on ballot 1, 2, 3, etc., and revisiting rule 40(b) is not included. If there is some authority for going back to 40(b) after balloting has started, I would be interested in reading it but as I understand it, Rule 40(e) doesn't give the chairman authority to do anything but call another ballot.
Also notice 40-b says president and vice-president.. clearly in 2012 Ryan did not get a majority of 8 delegations before the convention...