I think this is what I am...this is what it is for those who don't know...source: http://en.wikipedia.org/wiki/Sedeprivationism

Sedeprivationism is an ideological school or party of the traditionalist Roman Catholic movement that holds that Popes since John XXIII have been defective Popes, following the principles of the late French theologian Michel Louis Guérard des Lauriers, O.P., as Lauriers set it out in his thesis published in the Cahiers du Cassiciacuм and therefore called the "Cassiciacuм thesis".

According to Laurier's thesis, Popes John XXIII, Paul VI, John Paul I, John Paul II and (implicitly) Benedict XVI and Francis were or are defective Popes in that, due to their supposed espousal of the "modernist heresy", their consent to become Pope was faulty or defective, so that they became potentially Pope, but did not attain to the papacy.

This idea is also described in another manner by saying that they became Pope materially but not formally (the formula, "papa materialiter non formaliter").
Two consequences flow out of this thesis:

There is no real sede vacante since a man fills the role of potential Pope;
If the current potential Pope recants from Modernism and returns to Catholicism, he will complete the process and attain to the fullness of the papacy.
The terms sedeprivationism and sedeprivationist were coined by the late English Sedevacantist William J. Morgan.

Besides the late bishop Michel Guerard des Lauriers, O.P., those Traditionalists prominent for subscribing to this explanation are: Bishops Robert F. McKenna, O.P. and Donald Sanborn in the U.S.A., and Fr. Francesco Ricossa and his Istituto Mater Bonii Consilii (alternative name Sodalitium Pianum), to which Bishop Geert Jan Stuyver belongs, located in Flanders as well as the cities of Turin and Rome in Italy.

Sedeprivationism makes a lot of sense to me.  It seems to "resolve" the problems with both the ipso facto depositus and ab ecclesia deponendus schools of thought, both of which had some problems.

Besides, it's very hard to go against the academic credentials of Bishop Guerard des Lauriers.

Of course, I actually don't think we're in a sedeprivationist period because if Cardinal Siri was actually elected in 1958, then these popes are not even canonically legitimate, which would mean that they're not even material popes.

There's the prophecy from St. Francis of a non-canonically elected pope wreaking havoc in the Church.  I also am of the mindset that God would convert a material pope to the Faith upon election.