This is a pretty well documented "problem" and there are tons of threads on it.
Basically, there's really nothing wrong. Some people have "fixed" this problem by using fully synthetic oil or using GP style gear shifting.
Other than that, my only advice to you is to make sure you use enuf force while going from 1st to 2nd. Everyone on here has complained about it going into N, so it shouldn't be a technical issue. It's happened to me tons of times.
If you want more info, just use the search button. There are like 100 threads dedicated to this.