Did u try any other usb port ?

And when u hav plugin iPad , does iPad shows that it is charging ?

If it is not charging when you plugged it in , a few things might had turned up :

1.Driver problem

2.Usb port problem

3.The cable problem

4.The worst - iPad problem (if all the above is not the case)

But , i wanted to ask , you connect the iPad to the computer via 1-1 usb port or you use USB hub ?

Hmm , this will either be usb port problem or driver coz iPad does not charge when you plug it in