Modal dialog in Premiere Pro (using AE SDK)

Question

Hello all,
I have a plugin that does some long, intensive processing inside a single render call. I show my own progress bar in a modal dialog while this happens.
This is working fine in After Effects, but it's causing a crash in Premiere Pro. I get a few messages through the WndProc but then they just stop coming. I've attached some code below. Does anyone have any idea what might be going on there?
many thanks for any help,
Hugh
Here's the code that creates the dialog:
//assume host window is foregrounded
hostWindow = GetForegroundWindow();
// also tried HWND hwnd; PF_GET_PLATFORM_DATA(PF_PlatData_MAIN_WND, &hwnd);
hDlg = CreateDialog(theDLL, MAKEINTRESOURCE(IDD_PROGRESS), hostWindow, reinterpret_cast<DLGPROC>(DlgProc));
SetWindowLongPtr(hDlg, GWLP_USERDATA, (LONG_PTR)this);
CenterDialog();
ShowWindow(hDlg, SW_SHOW); UpdateWindow(hDlg);
SetForegroundWindow(hDlg); BringWindowToTop(hDlg);
hProgress = GetDlgItem(hDlg, IDC_PROGRESS1);
SendMessage(hProgress, PBM_SETRANGE, 0, MAKELPARAM(0, total));
and here's the window proc:
static LRESULT CALLBACK DlgProc(HWND hWndDlg, UINT Msg, WPARAM wParam, LPARAM lParam)
ProgressDialog *myOwner = (ProgressDialog*)GetWindowLongPtr(hWndDlg, GWLP_USERDATA);
switch(Msg)
case WM_INITDIALOG:
        case WM_WINDOWPOSCHANGING:
return TRUE;
case WM_NCLBUTTONDOWN: //prevent user moving the dialog box
if (HTCAPTION == wParam) return TRUE;
else return FALSE;
case WM_COMMAND:
switch(wParam)
case IDOK:
return TRUE;
case IDCANCEL:
myOwner->cancelled=true;
return TRUE;
break;
return FALSE;

Answer 1

Here's the code that is called periodically inside my processing to run the message pump, in case that's helpful:
SendMessage(hProgress, PBM_SETPOS, pos, 0);
HWND hProgText = GetDlgItem(hDlg, IDC_TEXT_PROG);
std::stringstream myStr;
myStr << "Frame " << pos << "/" << total;
SetWindowText(hProgText, myStr.str().c_str());
MSG Msg;
SendMessage(hostWindow,WM_ENTERIDLE,0,0L);
while (PeekMessage(&Msg, hDlg, 0, 0, TRUE)) {
if (!IsDialogMessage(hDlg, &Msg)) {
TranslateMessage(&Msg); DispatchMessage(&Msg);