Unhandled exception: 0x80000001: Not implemented. (VC++)

I am using MS Visual Studio 2005 (C++)..

Could anyone tell me what could cause a runtime exception like so..?

Unhandled exception at 0x07ed0027 (xxx.dll) in yyy.exe: 0x80000001: Not implemented.

xxx.dll is a dll i am working on and yyy.exe is an exe that is calling that dll.. When the undhandled exception comes up while debugging, it takes me to a function but I can't see anything wrong with the function (it doesn't raise the exception everytime this function is called). Anyway, I checked all the values in the function and they seem ok.. If I click continue instead of break, or press F5 after the break, then it goes on like nothing happened.. Please let me know if I haven't supplied enough information..

Thanks.

Like the more familiar 0xC0000005, 0x80000001 is the code of an exception that's being raised. You can look them up in winnt.h. In this case, I've found #define STATUS_GUARD_PAGE_VIOLATION ((DWORD )0x80000001L)

Guard pages are used for stack growth. The first page after the top of the stack is marked as a guard page. When you write to that - typically by pushing more data on the stack - a guard page exception is taken. The OS allocates an extra page or RAM (or perhaps 2 - details left to the OS) and moves the guard page up.