I did some other experiments, so I have some more details for you. BTW I'm running Windows 7 N and e1.4.2 version of the game.
link to screenshots
1. This issue
only occurs when
the right monitor is set to
primary in windows and the game window is on my left monitor. So the game works fine on my right monitor when the left one is set as primary.
2. When I change in-game settings to launch on the left monitor and manually move the game window to the right monitor the UI starts working again.
Now to your questions. When I have the game opened in windowed, load a save and move it to the left monitor while right is set as primary
3. I can't rotate or move camera on map with my mouse. Keyboard controls works fine.
4. When I move to a settlement on the right monitor and move the game window back to the left monitor, I can't click anything. Cursor changes to the crossed circle you get when you want to go to inaccessible terrain.
5. When I click on the game map the game appears to think I'm clicking always at the exact same spot (see screenshot1 I took it by clicking and pausing immediately, I think it would be exactly on the top edge of game window if I click-paused perfectly) no matter where my cursor actually is.
When I opened my game on windowed about in the middle of my two screens (see screenshot2) and experimented a bit, I noticed the following funny stuff happens:
6. When clicking on my left monitor (to the left of start quickbar) position of where the game thinks cursor is changes, depending on how fast I move the cursor from right half to left half. Faster I move the further left game thinks the cursor is. Until I leave the game window with the cursor and join again the cursor position doesn't change, so that's why I can't control the camera with it. The game doesn't see the cursor moving. When I move the cursor very slowly, the game actually thinks its directly under the right edge of my start quickbar (which is on the right monitor) or probably one pixel to the right of it, in the last specific place the game remembers before I left to the start quickbar and then left monitor.
7. When I leave game window with the cursor and move the cursor back on the game window on my left monitor the position again seems to be somewhere on top of the game window and always the same.