I got some crash reports recently, for some work in progress iOS app that I distributed to my clients via an IPA. To my surprise the reports fail to symbolicate, hence are pretty useless in hunting down the root problem.
I never had this problem before, and its occurrence seemed to coincide with my recent move to using the Xcode 4.0.*. Doing some Googling uncovered a post with a bit of background regarding this issue. It turns out that the newer versions of Xcode changed the way IPAs are built, and in the process broke the symbolication. D'oh !
Now, as a rule, whenever I upgrade stuff I try keeping a copy of the old version, as a precaution. Luckily I have an Xcode 3.2.5 still installed, as a fallback mechanism. All I need is to rebuild my IPAs using the older version of Xcode, until Apple fixes their tools. The post quoted above suggests fixing the Perl script that causes the problem. I'm not sure about that. It may work for a particular version of Xcode, as a last resort, if you really need Xcode 4.0.*. Falling back to Xcode 3.2.* seems a simpler, safer alternative, at least for my needs.