Why is Instruments preventing objc_msgSend crash

I have a crash from releasing an object too many times and calling it after it has been released. When I run with instruments, it doesn't crash.

开发者_C百科

Any Ideas why this might happen?

Im running Lion with Xcode 4 btw.

---

Turns out I had Garbage Collection ON for release mode and OFF for debug mode. I set my Analyze Run settings to release so GC was properly retaining and releasing when running Instruments, but debugging there was no GC.