SaveBarState fails when it is called from a thread

Hi,

In my application, I use SaveBarState() for persisting control bar
state.
The code fragment is something like this.

void CMainFrame::OnSavePersistance()
{
    SaveBarState(_T("My Persistence"));
       // Saves some information to an xml file
}

Since my xml saving takes some time I changed the code to execute in a
thread

UINT ThreadFn(LPVOID pParam)
{
    CMainFrame* pThis = (CMainFrame*)pParam;
    pThis->SaveBarState(_T("My Persistence"));

    return 0;
}

void CMainFrame::OnCntrlbartst()
{
    AfxBeginThread( ThreadFn, this );
}

But, now in the thread function SaveBarState() fails. It shows some
assertion in debug version. I think it is due to some mismatch in
MODULE_STATE.

statck trace for assert
CWnd::AssertValid() line 879 + 25 bytes
CControlBar::AssertValid() line 976
CStatusBar::AssertValid() line 732
AfxAssertValidObject(const CObject * 0x00431510 {CStatusBar
hWnd=0x00180c7e}, const char * 0x5f4ccfe8 THIS_FILE, int 531) line 108
CControlBar::GetBarInfo(CControlBarInfo * 0x00433d70) line 534
CFrameWnd::GetDockState(CDockState & {CDockState}) line 520
CFrameWnd::SaveBarState(const char * 0x0041844c `string') line 443
ThreadFn(void * 0x00431450) line 174

How can I avoid this problem?