They ran the sessions in 2005 on Saturday afternoon then Sunday morning.
As a system, it copped an unfortunate one with its first outing, when it pissed down half way through the Saturday session. Since the times had been decided by the running order in the previous race (2004 Brazil), it meant that those that ran in the dry (i.e. finished 9th-14th in Sao Paulo) got a massive advantage. Michael Schumacher (7th) in particular had to set his time in a rainstorm.
Sunday qualifying was considered rather pointless after all that, Schumi didn't even attempt to overturn his 27 second deficit on Fisichella.
That one is the problem with single-lap. (And why simply giving the drivers the choice of when to run solves the problem with single-lap.)