Windows became transparent intermittently using wbocx skinning control with multiple monitors

We’re experiencing skinning related issue among the WinForm or MFC dialogs in our application. The strange behavior occurs intermittently when using skinning OCX control with multiple monitors and could be easily reproduced in one of the WinForm dialog after repeating opening/closing it many times.

During the initial investigation phase, the observed behavior was that the application was non-responsive, suggesting the modal dialog just launched has gone behind the parent window. 

However, by using additional diagnostic tools, we confirmed this was not the cause.  The modal dialog is still properly chained to the parent, so it is not being shown behind some other window.  Instead, the actual behavior is that some or all of the dialog is transparent, but still very much in a modal state.  Sometimes, the entire dialog is invisible.  Other times, all but the patient banner at the top of the dialog is invisible.  There is another example where only the non-client area (i.e. chrome) is transparent.

The current version of the OCX is 7.0.8.4(9/6/2012). The OS is Win7 (32bit or b4 bit). We tried previous versions i.e. 5.0.9.4(8/7/2010) and version 7.0.2.1(2/8/2011) but it still reproduced.

Note that there’s no issue when single monitor is being used.  Anyone else has encountered the similar/same issue before?