SeaMonkey, thanks a lot for your quick reply. Even if this problem still exists it's nice to know that I'm not the only one with this.
Thank you also for the tip regarding map usage in order to work around this problem. I already thought of something like this, but it's nevertheless a bit disappointing that even the next unit button (not key) isn't working properly. Maybe I'm just a bit frustrated cause I used to cycle through all my units in those other games I mentioned (5 star series).
So one last question: Is there anything else I should know concerning this problem before continue playing/starting a campaign? I mean are you still playing the game this way (using only the map to detect units which are still available for action)?
Again, thanks a lot for your help! And sorry for any mistakes regarding my language/writing -- I'm from Germany and always need some practice before it gets better