I was having trouble with the very first exercise "Hello World" where we had to simply make the iPhone show Hello World on the screen. I couldn't really explain my problem since I am new to Xcode and Interface Builder but I clicked, double clicked and I STILL couldn't see the View window in Interface Builder.
Luckily I can say "I was"... meaning I've fixed the problem! It is strange that I seemed to be the only one in class with this problem... even re-installing four times hadn't fixed the issue...
So anyway... here's what I did to fix it:
In IB: Window > Document Info.
Deployment Target was set to "Default - iPhone OS 3.2" and Development Target" was set to "Interface Builder 3.1" (which was not the default). So I changed it so both were set at Default. I saved and closed IB and when I opened it again with the xib file the View window just popped up!!!
It's a beautiful thing!