Opticreep wrote:

But that still doesn't make sense. I don't think the signal-to-noise
ratio should be affected so drastically from this one little mistake.

What you think has no bearing on physics. Mispairing the signals
eliminates essentially *all* of the noise immunity that's designed in to
Cat5 cables. This is undoubtedly the source of your problem and why we
always recommend buying commercially manufactured patch cables rather
than making them yourself (or having a friend make them).

And besides, why would this 24-ft CAT5e cable work between a DSL
straight to my PC, but *not* work between a router and a PC? Maybe it
has to do with signal strength or the different impedences, but
thinking too much makes my head hurt.

More likely it's because your DSL modem only supports 10BaseT, so your
PC to DSL modem connection is only running at 10Mb whereas the router
and your PC probably both support 100BaseTX and thus are trying
(unsuccessfully) to run at 100Mb when they're connected together.

-Larry Jones

I hate it when they look at me that way. -- Calvin