Has it been raining in Melbourne? (Probably a silly question)
What you are experiencing may be due to moisture on an electrical connector somewhere which is tracking from 1 pin to another. One of the things Toyota did was to see if mine had had a new windscreen fitted at any stage as water sometime leaks around the windscreen then runs down the wiring harnesses and congregates around electrical connectors causing slight leakage across pins which upsets ECU's.
I have just ordered a scangauge
http://www.scangauge.com/ for mine, but don't know if it suits or not, the 05 petrols work with this but not sure about mine
Pull all conectors on the tranny and blow them out with compressed air then spray with a bit of WD40 and put them back. (I would also be checking the engine ECU, throttle position sensor, throttle body sensor etc.
1 thing you could try, it is a pain I know, is to dry out the inside of the vehicle.
This of course may or may not do anything for your problem.
First, ensue your A/C drain is clear, it will be on the left firewall, a small black tube about 1cm dia sticking out of a grommet about 2.5cm.
Whenever you drive the car have the aircon on flat out and recirculated air. You can mix warm air via the control to keep the cabin warm.
You could place a blow heater on the passenger and driver floors blowing under the dash and heat up the whole vehicle, then run you air con flat out etc.