Standing rules of the Senate
Chapter 22: Precedence of Motions
""Is it the sense of the Senate that the debate shall be brought to a close?" And if that question shall be decided in the affirmative by three-fifths of the Senators duly chosen and sworn -- except on a measure or motion to amend the Senate rules, in which case the necessary affirmative vote shall be two-thirds of the Senators present and voting -- then said measure, motion, or other matter pending before the Senate, or the unfinished business, shall be the unfinished business to the exclusion of all other business until disposed of. "
I know the Senate rules are mind-numbingly complicated, but come on!
Legislation: 3/5 of those sworn (60) to end debate (break a filibuster).
Rules change: 2/3 of those present and voting to end debate (break a filibuster).
This doesn't apply to a ruling from the chair that judicial filibusters are Constitutionally out of order.
All that I can do is report, you can decide.
The Senate, in 1975, changed the rules on the number of votes needed for cloture and they did it, after a number of parliamentary maneuvers, on a simple majority vote.
This was mentioned in a column in the Washington Times on May 14, 2003 by Charles Hurt.
Check it out at:
http://www.freerepublic.com/perl/post?id=934702%2C134