I have just followed through this thread. For the record (and for the information of those painstakingly researching a solution to that perennial problem that Toyota insensitively refuses to address), we have been enduring that unsanitary smell ever since we owned our brand new Vios in Dec 2007.

1. We don't use air fresheners as we know these to be detrimental to the normal function of car airconditioners.
2. We don't expose our car to extreme weather conditions as our car has always been parked nice, shaded, and safe in a shaded garage at home and at work; no, it wasn't exposed to any flooding.
3. We are frustrated to have left the unit several times for servicing with Toyota for several days at a time with the Toyota SA pretty convincingly acting out "surprised" at why our car is like this but to no avail.
4. We are disgusted at the recourse of needing to buy this or that just to address a problem that isn't supposed to be there or isn't our fault.
5. We are disgusted at the SA's requirement to inconvenience us with the procedure setting the a/c to fan just to dry the system a couple of minutes prior each time we bring the car to a park.
6. And so we have just ENDURED THIS STINKY AIRCON all these months as we realize that we are consumers helpless to the selfishness of Toyota.

Therefore, we conclude that the km check ups we oh so conscientiously try to keep up, with exorbitant costs and with schedule-bending appointments, are just a ploy for car dealers to make more money. The defective aircon and a host of other perennial Toyota problems are testament that they'll just further inconvenience you with car-less days and even extra charges at your attempts to invoke warranty. The 3-YEAR or 100,000 KM WARRANTY IS A BANE TO CONSUMERS as car dealers almost deliberately deliver defective units so you be sorry that you didn't subscribe to their profitable after-sales services!