I have been using a Nikon CoolPix 4800 with my Dimension 8400 for several months now with no problems.  I downloaded pictures 2 days ago-again with no problem.  However, today i tried to download more pictures and received the error message: Power surge on hub port- USB device has exceeded the power limits of its hub port.  I tried each of my USB ports and none of them worked.  I also checked the device manager which states that all of my USB ports are working properly.  Anyone else have a problem like this that can give me some tips?  Thanks!