Annoying Problem With USB Card Reader in Dell XPS 435T Solved Travis Phillipss Blog

Travis Phillips suggests:

So after about 2 – 3 hours of dealing with the crazy thing I found an obsecure post located here that said the issue was you need to disconnect the computer from the power.  Even if you turn this computer off the motherboard still gets power noted by the green light on the back that stays lit.  So I unplug the computer from the outlet, let the green light go out, and wait a couple of minutes.  I then power up the machine, let it boot up, and viola, my RealtekUSB 2.0 card reader was now working just as it always did.

via Annoying Problem With USB Card Reader in Dell XPS 435T Solved Travis Phillipss Blog.