Dodgy Brakes

[ooch12]

Has anybody experienced a problem with the T-sport snaking from side to side when braking? The problem seems to be intermittent i.e it may not happen for months and then all of a sudden it just happens once. It's my girlfriends car so don't know it inside out but it feels as though the electronic brake distribution system (The t-sport does have one doesn't it?) loses the plot. It's only happened once to me and at the time I was on a gently sweeping bend and wasn't even braking hard. I tried to recreate it several times after this but nothing. My girlfriend has had it happen when braking progressively in a straight line and it is frightening.

Could this fault be picked up by a diagnostic? Don't want to go to toyota only for the mecahnic to take it for a drive and it perform perfectly as it does 99% of the time.

The car is on an 05 plate and was bought from new.

Any help would be greatly appreciated as I think there is a real risk of driving the thing off the road if/when it happens again.