That 's exactly right. I should have focused on that immediately, as trying to track down the problem directly turned out to be next to impossible. (A very unexpected side effect of a minor unrelated "clean up" resulted in the dialog-close command becoming disabled. But there was no individual of that, either visible in the UI or in the "spy" window analyzer.
Anyway, the fix is in 6.5.1719.0, the links for which are in
this thread.