Stack frame incorrect on stack unwinding during exception

I'm tracking down a problem where we're running into an access violation
while unwinding the stack after throwing a C++ exception. From my
investigation it appears the stack frame is not correctly setup. Below is an
example of what I've observed.

When I enter my function Validate() (shown below) esp = 0x4d6f62c and ebp =
0x4d6fbf4. Then it does:

push ebp
lea bp, [esp - 0x894]

At which point esp = 0x4d6f628 and ebp = 0x4d6ed94. So the stack frame for
Validate's locals should be ebp = 0x4d6ed94. And in fact [ebp + 0x830] is
the 'this' pointer for Validate's STL string 'x' (when ebp = 0x4d6ed94).
However, when I throw an exception in Validate() it ends up in a little piece
of thunk code shown below:

lea ecx, [ebp + 0x830]
jmp std::basic_string::~basic_string()

The offset from ebp is correct, but the value of ebp is 0x4d6f628 which is
not correct. What happened? I did notice that this it the value of esp
after the locals were accounted for in Validate().

Snippets of code:
===========

#define T_OLEDB_ERR_DEADLY_STR(STR) do { Exception::raiseException(false,
STR, __FILE__, __LINE__); } while(0)

class TException
{
public:
    TException(const char *, int iExceptionCode = 0, DWORD dwIP = 0);
    TException(const char * pszMessage, const char * pszFileName, int
iLineNumber, const char * pszHostName, int iExceptionCode = 0);
    virtual ~TException();

    const char * GetMessage();
    const char * GetFileName();
    const char * GetHostName();
    const int GetLineNumber();
    const int GetExecptionCode();
    const DWORD GetInstructionPointer();

    static void InstallSEHandler(LPCTSTR sDir = NULL);

private:
    static TCHAR s_sDir[MAX_PATH];
    static void translate_SE(unsigned int u, _EXCEPTION_POINTERS* pExp);

    CStdString m_strMessage;
    CStdString m_strFileName;
    int m_iLineNumber;
    CStdString m_strHostName;
    int m_iExceptionCode;
    DWORD m_dwIP;
};

class Exception : public TException
{
public:

    Exception(HRESULT hr, bool bRetryable, const char * pszMessage, const char
* pszFileName, int iLineNumber, const char * pszHostName) :
        TException(pszMessage, pszFileName, iLineNumber, pszHostName), m_hr(hr),
m_bRetryable(bRetryable)
    {
    }

    void SetDBInfo(HRESULT hr, CComPtr<IUnknown> &m_spUnk);

    static void raiseException(bool bRetryAble, const char*pszMessage, const
char *pszFileName, int iLineNumber, HRESULT hr, CComPtr<IUnknown> m_spUnk,
CComPtr<IUnknown> pFI, CDynamicAccessor &acc);
    static void raiseException(bool bRetryAble, const char*pszMessage, const
char *pszFileName, int iLineNumber, HRESULT hr, IUnknown* m_spUnk, IUnknown*
pFI);
    static void raiseException(bool bRetryAble, const char*pszMessage, const
char *pszFileName, int iLineNumber, HRESULT hr, CComPtr<IUnknown> m_spUnk);
    static void raiseException(bool bRetryAble, const char*pszMessage, const
char *pszFileName, int iLineNumber, HRESULT hr);
    static void raiseException(bool bRetryAble, const char*pszMessage, const
char *pszFileName, int iLineNumber);

    HRESULT GetHR() { return m_hr; }
    bool GetRetry() { return m_bRetryable; }

private:
    HRESULT m_hr;
    bool m_bRetryable;
};

void Validate()
{
    std::string x;
    .
    .
    .
    if (x.length != 0)
        T_OLEDB_ERR_DEADLY_STR(x.c_str());
}

--
Thanks,
Nick