Tex37
This clogged fuel vent theory seems to be a recurring favourite here on Pprune.
It's certainly feasible in theory. At our airfield we had a case of a totally "imploded" fuel tank on a light airplane where the vent was iced up. Fortunately the forced landing was successful.
However, airliner tank vents are designed to cope with exactly that hazard. And I would also think it highly improbable that if vent clogging were to occur, it would happen in both tanks within seven seconds.
Further, I'd suspect that a vacuum strong enough to restrict fuel flow would also cause visible buckling on the wing skin, noticeable to any passenger who looks outside.
Just my $0.02