I'm pretty sure I've been clicking once, it may be the mouse pad thing on the laptop, if I was resting my hand on it when I click the button, it may be that it recognises it as a double click. BUT, there is no other NL sim open, only one opens.
How it happens is: I click to ride the coaster in sim, then it comes to the loading screen, only that only half of the loading screen is visible, the other half is off the side of the screen. When it then loads, it's in 800x600 resolution and all the settings are back to default, but once I click with the mouse or press a button on the keyboard it simply reverts to looking like the picture I posted in the first post. This is my NL settings, only the info bar obviously still believes itself to be in 800x600 mode.
This happens maybe once in every ten times I open the sim from the editor.
It sounds very similar to what has been said above, only no second sim is open... oh well, doesn't really matter, it's just slightly annoying
Edit: Just happened again;
Looks like it's gonna be something I'm just gonna have to put up with! heh. I noticed that it fudges up my FPS too.