need help for xib file

[xuUSA]

Hi I am having a very strange issue with xib file. Here is how I reproduced the problem (no coding involved, only settings):

step 1. created a tab-bar-app for iPad. By default there are two views (firstView and secondView) attached. I left them alone without a change.

step 2. created ThirdViewController.m (with .h and .xib), then attached the
thirdView to the app in IB. It worked well. (This step is optional. But
I did this step to show I knew the correct way in IB to add a new view to
tab-bar viewcontroller.)

Step 3. created FourthViewController.m (with .h BUT NOT .xib), and then
created FourthViewController.xib (for iPad) independently. After that,
I attached four view to the app. (EXACTLY same way as I did in step 2).
But the fourth view CRASHED app when I selected it!

Anybody had similar issue? Or you can do the steps above (in less than
2 minutes) and see what happens.

Any help?

Thank!

[xuUSA]

Forgot to mention: in step3 the xib file I created was "View Xib" under iphone/user interface (for iPad). The xib file itself looks fine as I am able to add labels inside.