I have a 24" and a 19" monitor in dual. The 24" is my primary monitor. When I enter Full-Screen Mode it works, but it maximises on the 19" screen! And I can't bring it back over to the 24"! 24" is set as my primary, and the window is maximised on this, but when I hit Full-Screen it just goes "nahhh, I'm going over to 19" to piss you off ;)"

Anyone else seeing this? Got a solution?

Interesting.  Working for me over here.  There must be something special on your end causing the issue.  Any floating windows involved?  Specific 3rd party plugs?  Does it happen with an un-modified "Normal" template?

Upgrade your graphics driver (not via Windows update, rather the site that makes your graphics card).

24" primary and 17" secondary here as well. I load the console view on the 17 and full screen X2 on the 24 and no problems. I can drag the console over on top for a closer view when needed and drag it back. Seems ok to me.

Solved.

I had my DVI cables plugged in the wrong way around so my 19" was monitor number 1 and the 24" number 2. I then had changed it so that number 2 (the 24") was the primary display.

What this means is that X2 is looking for which monitor is labelled number 1, and fullscreening to that. What it should be doing is looking for which monitor is the 'Primary' monitor. So not a bug as such, but something that might want to be tweaked to stop this issue occurring. Worth a quick little bug report?