SIGABRT error puzzling me

i am VERY new to objective-C. My only previous programming experience is with visual BASIC. So yes, i am a noob. But i am fairly intuitive and good with these sorts of things, so i am determined to learn. I decided after learning some basic to create a calculator program from scratch without looking at how to do it, and learn from the experience. I got it up to addition, and it worked beautifully. However, after i added subtraction and multiplication. it, to be blunt, took a shit. Immediately after running, it crashes and brings me to my untouched main.m file with the SIGABRT error. I have no idea what went wrong. the code looks like it should work to me, despite some organizational errors. So i tried commenting out everything i added, but to no avail. It still gives me the error. Any help would be appreciated thank you. Below are pictures of my code:

.h file: http://i73.photobucket.com/albums/i206开发者_开发问答/strbarrytree/ScreenShot2011-07-21at42338AM.png

.m file: http://i73.photobucket.com/albums/i206/strbarrytree/mycode.jpg

You have probably connected an outlet or action in IB and then you deleted the outlet/action in your header file. Check in IB if you have any connection with "!" next to it and delete it.