As Rojash suggests, ensure that the camera is powered by its mains adapter (assuming, of course, that it has one). Also ensure that the lead is plugged directly into a port on the PC (and not into a hub).
If that doesn't work, the simplest solution would be to buy a card reader. Lidl's have got a special offer, starting this Thursday (10 August), with a 24-in-1 card reader for just �7.99. (If there's not a branch of Lidl near you, there are plenty of other places which sell cheap card readers. Try Tesco Extra, Asda or online). [Card readers make the transfer of image files much quicker and easier. Even if you can find a solution to your current problem, it would still be worth investing in one].
Chris