xcode 3.1.3 thread_start error

I am currently working on an iPhone game and about 3 weeks ago I started receiving these strange errors that all originated from thread_start in the call stack. The weird thing is that the errors have been appearing on and off, and only recently have they reappeared after about a week. They also seem more likely to appear on t开发者_StackOverflow社区he device than on the simulator. One of the errors that I received today was an EXC_BAD_ACCESS in szone_free on the simulator, but after rebuilding my project and running the app ran fine, although it still crashed on the device. Does anyone have any idea what is going on here?