Hey, I had exactly same problem, loss of breaking power over a speed bump, I changed my break pad as well, it is not helping, it is until yesterday that i had to break suddenly at speed of 40miles/h, and it happened agian!!! i crashed into the front car, fortunately it wasn't serious, but it will happen when you need to break from high speed in a short distance, it is very alarming, please do ask a machnics to check it out!