With one particular Xcode project, my Xcode will launch, go through the usual startup (build, find working copies, etc) sequence then after the progress bar stops moving it abruptly quits. This section always seems to be in the crash logs:
Thread 18 Crashed:
0 libobjc.A.dylib 0x00007fff89eed118 objc_msgSend_vtable4 + 24
1 com.apple.Xcode.DevToolsCore 0x0000000111f81583 -[XCStringList appendElementsByTransferringFromStringList:] + 174
2 com.apple.Xcode.DevToolsCore 0x0000000111fc98cd +[XCStringList(Utilities) stringListWithDirectoryEntriesAtPath:relativeToPath:includedNamePatterns:excludedNamePatterns:directoriesOnly:followSymlinks:recursionType:includeTopLevelDirectoryItself:maxArgumentSize:errorPath:] + 2254
3 com.apple.Xcode.DevToolsCore 0x0000000111f52a6e -[PBXTargetBuildContext effectiveSearchPathsForSearchPath:] + 533
4 com.apple.Xcode.DevToolsCore 0x0000000111f52cd4 -[PBXTargetBuildContext _effectiveSearchPathsForSearchPathBuildSetting:] + 275
5 com.apple.Xcode.DevToolsCore 0x0000000111f6ff8c +[PBXCompilerSpecificationGcc2_95_2 headerSearchPathFlagsInTargetBuildContext:dashIFlagAcceptsHeadermaps:supportsSeparateUserHeaderPaths:] + 733
6 com.apple.Xcode.DevToolsCore 0x0000000111f70438 -[PBXCompilerSpecificationGcc2_95_2 standardFlagsInTargetBuildContext:] + 188
7 com.apple.Xcode.DevToolsCore 0x0000000111f743c1 -[PBXCompilerSpecificationGcc3_3 standardFlagsInTargetBuildContext:] + 55
8 com.apple.Xcode.DevToolsCore 0x000000011205c1a3 -[XCCompilerSpecificationClang standardFlagsInTargetBuildContext:] + 302
9 com.apple.Xcode.DevToolsCore 0x0000000111f719c1 -[PBXCompilerSpecificationGcc2_95_2 compileSourceCodeFileAtPath:ofType:toOutputDirectory:inTargetBuildContext:] + 3408
10 com.apple.Xcode.DevToolsCore 0x000000011205c063 -[XCCompilerSpecificationClang compileSourceCodeFileAtPath:ofType:toOutputDirectory:inTargetBuildContext:] + 1374
11 com.apple.Xcode.DevToolsCore 0x0000000111f6fb0a -[PBXCompilerSpecificationGcc computeDependenciesForInputNodes:ofType:variant:architecture:outputDirectory:inTargetBuildContext:] + 2360
12 com.apple.Xcode.DevToolsCore 0x0000000111fa8754 -[XCCompilerSpecification computeDependenciesForFilePath:ofType:outputDirectory:inTargetBuildContext:] + 2130
13 com.apple.Xcode.DevToolsCore 0x0000000112050090 -[XCBuildRuleDGSnapshot(DependencyGraphCreation) computeDependenciesForFilePath:ofType:forBuildFileReference:withOutputDirectory:additionalProperties:inTargetBuildContext:] + 7271
14 com.apple.Xcode.DevToolsCore 0x00000001120485a4 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) _computeDependenciesForFilePath:ofType:forBuildFileReference:usingBuildRule:inTargetBuildContext:processedPaths:] + 2349
15 com.apple.Xcode.DevToolsCore 0x0000000112048cd4 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForFilePath:ofType:forBuildFileReference:usingBuildRule:inTargetBuildContext:] + 112
16 com.apple.Xcode.DevToolsCore 0x0000000112049293 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForBuildFileReference:inTargetBuildContext:] + 1442
17 com.apple.Xcode.DevToolsCore 0x000000011203db43 -[XCBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForAllBuildFileReferencesInTargetBuildContext:] + 2019
18 com.apple.Xcode.DevToolsCore 0x000000011204ac89 -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesForAllBuildFileReferencesInTargetBuildContext:] + 48
19 com.apple.Xcode.DevToolsCore 0x000000011204b6fe -[XCSourcesBuildPhaseDGSnapshot(DependencyGraphCreation) computeDependenciesInTargetBuildContext:] + 2650
20 com.apple.Xcode.DevToolsCore 0x0000000111faab64 -[XCProductTypeSpecification computeDependenciesInTargetBuildContext:] + 976
21 com.apple.Xcode.DevToolsCore 0x0000000112039443 -[XCNativeTargetDGSnapshot(DependencyGraphCreation) computeDependenciesInTargetBuildContext:] + 3732
22 com.apple.Xcode.DevToolsCore 0x0000000111f49ebb -[PBXTargetBuildContext createDependencyGraphWithTargetDGSnapshot:] + 4798
23 com.apple.Xcode.DevToolsCore 0x0000000111f5bb62 -[PBXTargetBuildContext(DependencyGraphEvents) dg_setTargetSnapshot:] + 453
24 com.apple.CoreFoundation 0x00007fff88b8e90c __invoking___ + 140
25 com.apple.CoreFoundation 0x00007fff88b8e7a4 -[NSInvocation invoke] + 132
26 com.apple.Xcode.DevToolsCore 0x0000000111f5af48 -[PBXTargetBuildContext(DependencyGraphEvents) processDependencyGraphEvents] + 608
27 com.apple.CoreFoundation 0x00007fff88b8e90c __invoking___ + 140
28 com.apple.CoreFoundation 0x00007fff88b8e7a4 -[NSInvocation invoke] + 132
29 com.apple.Xcode.DevToolsCore 0x0000000111fa3de7 -[XCInvocationQueue _processNextInvocationInThreadSlotNumber:] + 381
30 com.apple.Xcode.DevToolsCore 0x0000000111fa41f9 -[XCInvocationQueue _processInvocationsInThreadSlotNumber:] + 525
31 com.apple.Foundation 0x00007fff83b671ea -[NSThread main] + 68
32 com.apple.Foundation 0x00007fff83b67162 __NSThread__main__ + 1575
33 libsystem_c.dylib 0x00007fff81b528bf _pthread_start + 335
34 libsystem_c.dylib 0x00007fff81b55b75 thread_start + 13
I've tried running the Xcode uninstall script and re-installing from the App Store, so I don't think my installation is the issue. I'm running OSX 10.7.1.
I re-created the project with git clone and I was able to open the project again. I suspect that the xcodeproject file was corrupted somehow, perhaps a bad conflict resolution.