Remember the first lesson in network troubleshooting

I have been running Vista RC1 5600 for some time now. I have been able to
connect to the Internet through the 3Com wired/wireless cable gateway but
was unable to see any of my other computers on the network, nor could I see
the Vista system from any of the others. I tried nearly every possible
combination of settings and tweaks, within Vista and the gateway, but
nothing worked. I started to notice the Vista system was sluggish and
downloads were taking a long time. Finally I did the thing I should have
done first. I unplugged the network cable to check it for damage. No damage,
but just for fun I tried a different (Cat 6) network cable. Now my network
speeds are back to normal and I can see and connect to all the other
computers on the network. The cable I was using was a flat style ethernet
cable designed for travel and was all I had available at the time.
I am almost embarrassed to post this. I am by no means new to networking,
but sometimes we overlook the simple things.