I've got exactly the same problem (2003 V6 Altise) - and it's driving me nuts!!! It's been into Toyota numerous times and they can't fault it - even when it's happening right there in front of them. Seemed to start after the dipper switch recall part was fitted. They eventually replaced the recall part which fixed the problem for about a year then it came back again. Slight flicker every now and then when you do something that puts a load on the system - eg indicate, brakes on etc. After a few weeks it gets to the point where power will momentarily drop right out when you do something, or when the AC switches itself on and off. Big safety problem at night because everyone in front of you or coming towards you thinks you're flashing your lights at them. Last week it was back at Toyota again, and as has been the case in the past they could see it happening, so they booked it in for a proper check to find the fault, I took it in for the booking a few days later and it didn't do it while it was there, and again they couldn't fault it so all they did was clean the earth points and check the connection of the recall part. All good for a few days then it came right on back! I'm reading a few different posts about this problem - time for another recall??
