I am a new user to mac..well about 2 years now, i have not encountered any problems until now!

I have an iMac and have leopard, suddenly my dashboard has stopped working, along with the hot keys...? i can't see what has made this happen and i cannot get it back? when i click on the dashboard icon nothing happens...

I have tries many things but have not got anywhere..does anyone have any suggestions?

The only way it does work is if i switch users...