I had a similar problem - the dryer had overheated and tripped the cut out - to cure it :
1 - make sure your filter is clear (bottom of front behind kick board)
2 - remove the lid of the machine
3 - you will see 2 trip switches on the top of the metal exhaust ducting. Each has a small, square button. If you press these they will click and reset. If they do not click the problem lies elesewhere.
Hope this helps
Mark Christie, February 2009