So I’ve had this problem off and on for the past couple of days while working on my latest iPhone application, but it seemed to come and go, so I didn’t pay much attention to it until today.
The problem got so bad, that I couldn’t do anything within xcode without it freezing up and displaying “unrecognized selector sent to instance” in an error popup dialog. I searched Google, and it seems that many people have experienced the same issue, but not to the extend that I was having. I finally stumbled upon a link that seemed to solve my issue: http://djuncas.blogspot.com/2009/03/unrecognized-selector-sent-to-instance.html.
It turns out that I had modified the method signatures of some files that were referenced from IB (Interface Builder); however, I didn’t upload those references, and so xcode didn’t know how to link properly. Although this was a mistake on my part, I feel that xcode should at least handle this exception more elegantly than freezing up. Props go to Mads Godvin Jensen for documenting the problem in his blog, and I’m echoing the solution as a way to remember this myself.