radio wont work?

i recently tried putting in a cigarette lighter so i would be able to charge my sat nav in my corsa everything was working fine until i put the stereo back in now the stereo flashes but dosnt actualy come on i cant switch it off either and the clock just has a dim light behind it and when i open my door the indoor light dosnt come on ive checked the fuses and they seem to be fine ive also disconected the lighter but to no avail what have i done wrong and how can i fix it please the car is a vauxhall premier 1997

many thanks
rory