Problem solved guys. It was a dodgy power supply. I just hooked up the new one and hit the max speed no problems. I got the old one off ebay too, I guess sometimes you ghet a bargain, sometimes you get stung. Thanks for the help anyway!
Balsaman, I understand about the geckos keep raising the voltage until there is no more, but surely this is why we fuse things? I don't understand enough about electronics to start an argument, so don't think that's what I'm doing, I just like to understand things as best I can.
