The nipples ends are butting into the edges of the holes. Slow down and don't try to rotate the hub and pull all the nipples through simultaneously. With one hand twist the hub. With the other, use a screwdriver to wiggle a nipple that's not through, then the next, then the next. Just one or two of the nipples are hung up. Just work around the wheel methodically until you find the nipple that's stuck. Once you free that one up, the hub will suddenly twist some more. Then another nipple may be hung up. Usually no more than a couple though.
To avoid this, I start with the first key-spoke and the next one going one way, then immediately twist the hub and insert a crossed spoke going the other way to keep the hub twisted. Then lace up all the other spokes in the original direction. Also be sure to start with all the heads-out spokes first.
Last edited by DannoXYZ; 04-14-11 at 12:05 AM.