I've seen compiler bugs, too, but the only way I've ever found them, and fixed them, is by doing what JMC said. There's no getting around setting a breakpoint and stepping through the code. If the problem just goes away without you changing anything, then that was a glitch in the compiler generated code. Those are mighty rare, though, and it is more likely that you'll find that the inputs are not the same as you thought they were. I dealt with that kind of case just yesterday. It happens, and only stepping through the code and seeing how things really are will show it.