It's always pretty much the same stack trace, and usually thread 0.
Code:
0 -- 0x96bbf6e8 -- _objc_msgSend
1 -- 0x90c2f054 -- -[_NSUndoStack popAndInvoke]
2 -- 0x90c2ee57 -- -[NSUndoManager undoNestedGroup]
3 -- 0x94ee1e56 -- -[NSApplication sendAction:to:from:]
4 -- 0x94f907cc -- -[NSMenu performActionForItemAtIndex:]
5 -- 0x94f904d1 -- -[NSCarbonMenuImpl performActionWithHighlightingForItemAtIndex:]
6 -- 0x94f90157 -- -[NSMenu performKeyEquivalent:]
7 -- 0x0005160f -- -[OWBrowserWindow performKeyEquivalent:]
8 -- 0x94f8e874 -- -[NSApplication _handleKeyEquivalent:]
9 -- 0x94eabb36 -- -[NSApplication sendEvent:]
10 -- 0x00289490 -- -[OAApplication sendEvent:]
11 -- 0x94e090f9 -- -[NSApplication run]
12 -- 0x00285fcb -- -[OAApplication run]
13 -- 0x94dd630a -- _NSApplicationMain
14 -- 0x00010978 -- _main
15 -- 0x00002dc2 -- __start
16 -- 0x00002ce9 -- start