Dialog not displaying

If I have a CAknSingleNumberStyleListBox dialog
on display and call the following dialog
it is not displayed:

CAknMessageQueryDialog* dlg = new CAknMessageQueryDialog(CAknQueryDialog::ENoTone);
dlg->PrepareLC(R_ABOUT_BOX);
dlg->RunLD();


However,
If I 'first' call:
TBuf<20> dummy(_L("dummyDlg"));
CAknQueryDialog* dlgDummy = new CAknQueryDialog(dummy, CAknQueryDialog::ENoTone);
dlgDummy->ExecuteLD(R_HACK_MSG);

..and then immediately call:
dlg->RunLD();

..the dlgDummy is not displayed, but dlg is as I expected
in the first place!

The hack works fine on the emulator and on my 3650
device but I hate using hacks. Any idea what the problem
is and how to resolve it without the hack?

cheers,

Paris.