So... here's the sp. I've bought a house and all the rooms have Cat 5
cable already in place. The wall sockets are labelled 568B on the
inside and, in order, the wire pairs are BLUE/ORANGE/GREEN/BROWN. All
the cable runs go back to the attic but the previous owner has removed
the patch panel and so all the cables are now unterminated. I believe
that ethernet uses the 2nd and 3rd wire pairs so, for 568B, pins 1,2,3
and 6 should be w/o,o,w/g and g. Pins 4,5,7 and 8 should be
bl,w/bl,w/br and br.

I'm cheap and I don't want to pay for a new patch panel.

What I want to do is simply attach RJ45 plugs to the unterminated ends
and plug them into a cheap switch but... if I wire the plug to either
the 568B or 568A pattern it fails. I know that the switch is sound as
I've tested it working using cables I made up - which also suggests I'm
using the crimps correctly - so what am I doing wrong?