The test system I'm working with didn't have either MSCOMCTL.OCX or MSCOMCT2.OCX.
My system had MSCOMCTL.OCX, so I copied this file to the test system and registered it.
My VBA programs now work as expected.
Thank you for your help.
Although I'm concerned that this might have un-done the Microsoft security update.
I have also started a trouble ticket with AutoDesk regarding this problem. I'm very curious to see what they have to say about this.
Thank you again,
the following solution for this issue has now been posted on the AutoCAD Knowledgebase:
Error "Object Library invalid" when running VBA applications
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