I was checking the return codes defined in WinNT.h, and STATUS_BREAKPOINT was defined as 0x80000003, and is one that I have encountered often enough. It tends to occur deep within standard library code, when the library detects that something is messed up. Often this seems to be caused by overwriting memory accidentally (buffer overflows, using deleted pointers, etcetera). It's essentially a breakpoint that is hardcoded into the library that under normal circumstances should never get excecuted.

I don't know if this is what your debugger is referring to when it says 03, though. Just my best guess. VC++6 will actually stop execution and show you the line of code where the error occurred, though it is almost always in assembly code. You do get to look at the call stack, however, and see which function called a standard library function, which ultimately led to this problem. That is often very useful information. I don't know if your debugger could easily provide such information, and if so, how, but I would think that it is quite likely capable of it. Going into debug mode on an assembly break point instruction and being able to view the call stack both seem to me to be very important things for a debugger to support.