Enumerating Windows

Hey There,
    I have this function that is called through EnumWindows:

BOOL CALLBACK EnumOpenWindows(HWND hwnd, LPARAM lParam)
{
    DWORD dwID;
    LPDWORD dwID2;
    LPDWORD currProcId;
    FILE* fp;
    struct _HwndProcStruct* locHPStruct;

    fp = fopen(THREAD_LOG_FILE,APPEND_MODE);
    fprintf(fp,"*******************<EnumOpenWindows>*******************\n");
    fclose(fp);

    dwID2 = (LPDWORD)calloc(1,sizeof(DWORD));
    locHPStruct = (struct _HwndProcStruct*)lParam;
    *currProcId = locHPStruct->procID;
    *dwID2 = 0;

    GetWindowThreadProcessId(hwnd, dwID2);

        fp = fopen(THREAD_LOG_FILE,APPEND_MODE);
        fprintf(fp,"currProcId=%d dwID2=%d\n",*currProcId,*dwID2);
        fclose(fp);

    if(*dwID2 == *currProcId)
    {
        locHPStruct->WindHandle = hwnd;
        free(dwID2);
        return FALSE;
    }
    else
    {
        free(dwID2);
        return TRUE;
    }
}

I'm using it to try to find the HWND from a Process ID. For some
reason, when I have the file print statements below
"GetWindowThreadProcessId(hwnd, dwID2); " the function will generate
the following error:

Unhandled exception at 0x0040126c in SysTrayApp.exe: 0xC0000005: Access
violation writing location 0x000809be.

But if I comment out those three lines, then the function executes
normally. What could cause this?

-Jay
(patelj27b at gmail dot com)