I had the exact same problem recently, however I am not entirely sure the cause is the same. What I can tell you though is what resolved the issue for me (although I'm still not entirely satisfied with the solution).
In the end, it seems like a compiler issue, and this might confirm what others have said about compiler optimization.
I am using Xcode 4.0 (build 4A304a). The issue was with LLVM compiler 2.0 Code Generation. One key in particular: "Optimization Level"
Debug was set to "None".
Release was set to "Fastest, Smallest"
Changing Release to "None" fixed the crash (and similarly changing Debug to "Fastest, Smallest" caused the app the crash on launch).
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