PF> Here is a simple wrapper for WinPostMsg that will fix the problem
 PF> (as long as it is used between threads,  not for posting to the
 PF> same thread (which is not often done)):

 BOOL PostMsg (HWND h, ULONG msg, MPARAM mp1, MPARAM mp2) {

   BOOL rc = WinPostMsg(h,msg,mp1,mp2);

   if(!rc) {

     PIB *ppib;
     TIB *ptib;

     if(!DosGetInfoBlocks(&ppib,&ptib)) {

       PID pid;
       TID tid;

       if(WinQueryWindowProcess(h,&pid,&tid)) {
         if(pid != ppib->pib_ulpid || tid != ptib->tib_ptib2->tib2_ultid) {
           for(;;) {
             DosSleep(1L);
             rc = WinPostMsg(h,msg,mp1,mp2);
             if(!rc) {
               if(!WinIsWindow((HAB)0,h)) /* undocumented but seems to work */
                 break;
             }
             else
               break;
           }
         }
       }
     }
   }
   return rc;
 }

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