After some intensive detective work I discovered on my own that the issue I described in my original post was being caused by SecureAge software which I had installed a week earlier or so. Since I did not like SecureAge popups, I disabled it in a startup settings, thinking that this should not have any impact on my computer. Wroooooong.
It had, and it caused me a lot frustration when I was trying to install Iris, as it kept throwing at me the blooming message I mentioned in my first post above.
Disabled it was, but still causing me trouble. Nasty piece of programming.
I hope my finding will help some people who might experience a similar problem.
Iris had nothing to do with my problem. On the contrary, it helped me discover a serious issue caused by disabling SecureAge software in the startup settings. The only qualm I have about Iris is that it doesn’t allow you to choose the path where you want to install it. That’s a serious shortcoming.