There once was a little guy who networked offices. He had this job with 30 computers. Everything went fine (what a relif!). He went back a week later to add one thing, and all of a sudden one machine wasn't connecting to the Novell server. Hmmmmmmm this was weird. He tried everything he could think of for 3 hours. Then he finally looked to see if the computer had an IP address. It did. He pondered, how can he have an ip NAT'ed to him if he wasn't connecting to the network. After exausting all options, he changed the RJ45 Cat5 wire. And poof! Everything magically worked.
The moral of the story...
Dont buy cheap wires!