So, I got a new computer (to work on it), and installed Ubuntu 11.10 on it. As my home computer is not strong enough (I'm using some strange mix of Xubuntu/Ubuntu/Kubuntu there), this was my first real contact with Unity.
And somehow (I don't really remember how) I managed to have my favorite browser (Opera) on the screen, but neither in the side bar (which, as I understand, should contain icons for all currently running programs, as well as some icons to start more programs), nor in the Alt+Tab window list.
The green mark is proof that the browser window in front is really Opera, while the yellow marks show how Opera is missing in both those lists.
Closing and restarting Opera seems not to help. In this screenshot, I have only Opera and two terminal windows (one out of sight), but normally I have enough windows to fill the whole two screens, which makes it a bit difficult to find the Opera window if it is obscured.
What could have caused this, and how I get my icon back?
(Actually, I'm considering changing the window manager completely, but I'll first try to solve this problem and see if I can get used to Unity.)