I’ll often open up the Design Help database from an icon on my workspace as I’m used to that help and can find the information I want a lot faster then the Help that’s inside DDE. I get the error message when clicking on something such as the “IsOpen” link under NotesDatabase, as shown below.
I don’t always get the message but it’s fairly often.
I had a user who experienced the same error while starting Lotus Notes 8.5. The solution was to have Notes cycle through this prompt (my user had several), then select the ‘Window - Show Thumbnails’ menu option. Here you will see the Notes windows opened and active. Click the window in question, and remove from the list. Hope this helps.