Try this,
Plug the charger in and then push an opened paperclip ro something like it into the reset hole. Wait and then the device will switch on should spark into life.
You haven't loaded a new map by any chance before this started to happen? If so you will have to contact TomTom to register it (assuming you paid for it!).
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix satellite navigation.