0 com.apple.Xcode.DevToolsCore 0x006da50a _symbolKeyForValue + 206
1 com.apple.Xcode.DevToolsCore 0x00833163 -[PBXProjectIndexBTree initWithContentsOfFile:comparisonFunction:keyForValueFunction:context:] + 474
2 com.apple.Xcode.DevToolsCore 0x006db749 -[PBXProjectIndex readDataFromFile:] + 1468
3 com.apple.Xcode.DevToolsCore 0x005bb49c -[PBXProjectIndex initWithProject:] + 360
4 com.apple.Xcode.DevToolsCore 0x005bafe4 -[PBXProject loadIndex] + 132
5 com.apple.Xcode.DevToolsCore 0x005bae69 -[PBXProject beginIndexing] + 61
6 ...ple.Xcode.DevToolsInterface 0x00b1bf33 -[PBXProjectDocument readFromFile:ofType:] + 486
7 com.apple.AppKit 0x90488d97 -[NSDocument(NSDeprecated) initWithContentsOfFile:ofType:] + 484
8 com.apple.AppKit 0x9048da6c -[NSDocumentController(NSDeprecated) makeDocumentWithContentsOfFile:ofType:] + 136
9 ...ple.Xcode.DevToolsInterface 0x00bd9cf3 -[PBXDocumentController _innerOpenDocumentWithContentsOfFile:display:didOpenWithExternalEditor:] + 689
10 ...ple.Xcode.DevToolsInterface 0x00bda0f2 -[PBXDocumentController openDocumentWithContentsOfFile:display:didOpenWithExternalEditor:] + 752
11 com.apple.Xcode 0x0000a35f 0x1000 + 37727
12 com.apple.Xcode 0x000067c8 0x1000 + 22472
13 com.apple.Xcode 0x00006798 0x1000 + 22424
14 com.apple.AppKit 0x9039d5bb -[NSApplication _doOpenFile:ok:tryTemp:] + 558
15 com.apple.AppKit 0x903e042a -[NSApplication openFile:ok:] + 56
16 com.apple.AppKit 0x9048b73c -[NSDocumentController(NSPrivate) _openRecentDocument:] + 127
17 com.apple.AppKit 0x90119b03 -[NSApplication sendAction:to:from:] + 112
18 com.apple.AppKit 0x901c8540 -[NSMenu performActionForItemAtIndex:] + 493
19 com.apple.AppKit 0x901c8245 -[NSCarbonMenuImpl performActionWithHighlightingForItemAtIndex:] + 220
20 com.apple.AppKit 0x901a5122 AppKitMenuEventHandler + 6608
21 com.apple.HIToolbox 0x96a03303 DispatchEventToHandlers(EventTargetRec*, OpaqueEventRef*, HandlerCallRec*) + 1181
22 com.apple.HIToolbox 0x96a0273d SendEventToEventTargetInternal(OpaqueEventRef*, OpaqueEventTargetRef*, HandlerCallRec*) + 405
23 com.apple.HIToolbox 0x96a1f092 SendEventToEventTarget + 52
24 com.apple.HIToolbox 0x96a5331d SendHICommandEvent(unsigned long, HICommand const*, unsigned long, unsigned long, unsigned char, OpaqueEventTargetRef*, OpaqueEventTargetRef*, OpaqueEventRef**) + 411
25 com.apple.HIToolbox 0x96a79b6f SendMenuCommandWithContextAndModifiers + 59
26 com.apple.HIToolbox 0x96a79b2c SendMenuItemSelectedEvent + 134
27 com.apple.HIToolbox 0x96a79a3e FinishMenuSelection(MenuData*, MenuData*, MenuResult*, MenuResult*, unsigned long, unsigned long, unsigned long, unsigned char) + 162
28 com.apple.HIToolbox 0x96a565cc MenuSelectCore(MenuData*, Point, double, unsigned long, OpaqueMenuRef**, unsigned short*) + 640
29 com.apple.HIToolbox 0x96a55fb7 _HandleMenuSelection2 + 383
30 com.apple.HIToolbox 0x96a55e2b _HandleMenuSelection + 53
31 com.apple.AppKit 0x900e1ad3 _NSHandleCarbonMenuEvent + 244
32 com.apple.AppKit 0x900488dc _DPSNextEvent + 1920
33 com.apple.AppKit 0x90047ca0 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128
34 com.apple.AppKit 0x90040cdb -[NSApplication run] + 795
35 com.apple.AppKit 0x9000df14 NSApplicationMain + 574
36 com.apple.Xcode 0x00002c82 0x1000 + 7298
I have solved it by deleting the MyProj.pbxindex folder, but thought others might find this info useful.
Matt Gough