Make sure you don't put the same color and color stripe together on the plug, they shouldn't all be together, follow the colorcoding in the webpage I linked, and make sure to push the wires in all the way into the plug. I generally pull the twisted pairs out further from the sheath before putting them into the plug, then push the wires all the way, then slide the sheath up into the plug before crimping. Sometimes the end wire doesn't go in far enough.
Have you tried the cable on a computer and USED it? An improperly made cable will show a link light, but won't be able to transfer anything reliably.