Strange problem with a 200w scooter.

Hi, I'm new to this forum so if I make a mistake just blast me.
I live in Melbourne, Australia and I own a 200w "Leisger QQ electric" scooter that I purchased from an Australian Ebay vendor in March '08. It has worked fine up until two days ago when, on a short ride home from my local shopping centre, the motor response suddenly became weaker and the speed dropped considerably. The battery was nearly fully charged and so this was not the problem. I stopped the bike and tried to see what was wrong. I couldn't see any problems and so I tried to ride away. The bike's motor would not start at all but the lights, power meter, horn and indicators still worked. I waited for a while and tried again. This time the motor seemed to start to work...there was a quick "jump" from the motor (like it was trying to get started) and then it stopped. It did this repeatedly. Because I was far from home I had to manually peddle. When I started peddling I tried the motor again by twisting the throttle. This time it started to work perfectly but as soon as I stopped, it would not start again, just making a noise like it was trying to work from a standing start and then failing, like a small jump when the throttle was turned on and then nothing. Once again I pedalled and once again the motor started working when I twisted the throttle and kept working perfectly until I stopped again. Then it started to just make the jumping noise or not work at all.

I have checked the brakes (they are not grabbing, the brake light is not on permanently or stopping the bike's wheels incorrectly), the fuse and circuit breaker...everything. As you can imagine, I'm pretty exasperated. The scooter's only done about 50km total travel and now I have something that no longer works that I really enjoyed using.
Could it be the controller? If so, how do I find where to change the controller...where is it located in the bike?