(updated)Help on Serial communication between Arduino and PC!!

PaulS:
These are contradictory statements, you know. If everything is working perfectly, it's time to quit. If not, the "everything's fine" is not true.

So, which is it? Going back and editing your original post is nor a good idea.

Sorry for any misleading, I am talking about the small data size case here, which is,

If I used intData[3], then everything is working perfectly, if I used intData[20], then the problem appears.
That's the strange part about it, with smaller data size, it actually works.

Also, I am not changing my original post, I simply added some stuff, this is not a good idea?