@Tuyen Nguyen: Have you installed the iOS 5 SDK on your Mac? I think this is what you need.
You also need to understand that some functions may not be available in some cases, as they are still a version of BETA. It may not be a fully functional version.
So, you can try using the iOS 5 SDK on your Mac, or if you have already tried this, I think you should wait until the final version of iOS 5 works correctly.
Also in the link below, they discussed that some iOS 5 features still do not work on iPod. So maybe Apple is working on it until the final launch.
http://www.ifans.com/forums/showthread.php?t=344401
You can also try to refer to this link. Maybe this can help you a little.
iPhone Dev: Xcode Debugger Doesn't Stop at Breakpoints
Hope this helps you.
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