In comp.dcom.cabling windsurferLA <ps144nyc@yahoo.com> wrote in part:
> When you asked about T-568A or T-568B, it triggered a memory.

That's the idea.

> Now doubting my wiring skills, I got out my jeweler's eye
> loop to very carefully look at both ends to make sure one had
> not be wired "A" and the other "B." The result was not what
> I expected. A careful examination of the newer end appears to
> reveal that the blue-white (#5) and the green white (#3) were
> inadvertently interchanged at that end and only that end.

This is the most common newbie wiring mistake. Swapping
the whites turns the layout into side-by-side and splits
the green and blue pairs.

> I expect that repairing the cable will solve the problem. WHAT
> I FIND SURPRISING is that the cable has worked with so many
> (guest's) computers for so long that it was not until the A -
> B question was raised that I thought to check the colors of the
> inner wires - a not so easy a task for old eyes like mine.

It is hard for everybody, and impossible with some cable
mrfs where the whites are unmarked (some plenum).

> Obviously, there is enough cross talk between the pairs to
> effect a connection with most, but not all, hardware.

Crosstalk is not really required. rememeber the signal is
differential and also present full-strength on the green.
Still, a bit surprising it ran as well as it did. Of course,
it never needed to carry more than 1 MBps, so retransmits
would go largely unnoticed.

> Although I feel rather stupid for not spotting the wiring
> error earlier, I never suspected a wiring error would be
> the problem.

Many years of experience have led to to _ALWAYS_ check the
cabling first. Especially if there is any indication it is
home-made. It is incredibly difficult to crimp connectors
correctly.

-- Robert