I had the same problem.It was caused by the slots at the back of the machine becoming clogged with fluff,preventing the hot air getting out.If clearing the slots dosen't do the trick,SWITCH THE ELECTRICITY OFF! Remove the "boot shaped" pannel at the back,you will see the element and two small thermostats try pressing the thermostats to reset it/them.Re-assemble and start.If that is no good you need somebody with a bit of electrical knoledge and a multi-meter.
john, February 2005