Both the case's USB connectors I used initially and the 6in1 reader
have 2 pairs of 4 wires for USB. I do not have the feeling this is the
issue.

A little known fact is a USB device is only loaded on the slot you
first installed it on. Some devices have ways of dealing with this
issue but many do not. Someone may reply that this info is false and
they have never had this trouble but YMMV.
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When your PC gives a little they give a lot.
http://www.dslreports.com/forum/disco