Why won't my ipod unlock?

I accidentally unplugged my ipod when it was blinkin the 'do not disconnect' thingy, an now it wont unlock even if I switch the little button on the top left hand corner. it's never done this before, how can I fix it?

Do you mean it won't turn on, is the screen blank?
Try these steps:
Toggle the hold switch about 5 times
Hold the centre button and menu button for 8 seconds
The ipod should then restart.