sandboxing interaction issue
Sandboxing (as introduced in OSX 10.7) doesn't like py2app's executable stubs, in particular the fact that the stub is not linked to the AppKit framework.
This can be seen bij creating a GUI application (using any GUI toolkit) with a file dialog (open/save), the application will crash when trying to show the dialog.
There is an easy workaround for the crash: recompile the executable stub and explicitly link with AppKit.framework.
That is a suboptimal solution though:
1) the stub code uses dynamic loading tricks to avoid linking to AppKit, those tricks could be removed
2) the dynamic loading tricks are there for a reason: without those tricks the application will trigger compatibility modes in system framework (that is, some frameworks behave slightly differently when the binary is linked with older SDKs).
The solution for that would be to recompile the stubs with every new OSX release. That should only be necessary for the 'intel', 'i386' and 'x86_64' targets (the other ones include PPC code)