Try powering up your laptop with the card already installed in the slot.
Whoops, I mis-read your post. Sorry. As already suggested make sure every other USB device is unplugged. If in the past you have hung some power hungry devices on your USB then you may have a power supply issue in your laptop. Excessive current draw from too many devices can cause permanent damage to the power source. Laptops seem to be especially vunerable to this cause of size limitations of the laptop, whereas a PC can house a much larger power supply with ample guts to handle many devices. Hopefully this has not happened to yours.