I still belive that something in your code caused the bahaviour. DO CASE is nothing to do with Excel object.
What I would recommend is to try to catch the moment where excel become minimized. I am afraid that debugging may not help here. You could:
1. Add a line like /wait wind time 2.0 trans(line())/ after each line in your code to follow the excel screen and see when it became minimized, or
2. Add a code
if .windowstate=xkminimized
* do something, like suspend, ?line(), etc...

>Dear Yuri ,
>
>Amazing! I never saw that after hours of debugging. I must have added that line during a cutnpaste operation from an excel macro, and overlooked the min for max. Sorry for that !
>
>However, I have removed the line. Still the same problem !
>
>Regards,
>
>Steve.