This problems has hunted me for years, always on my work computer, I can open an application Window, but when I move it to the right side of the screen it gets reduced automatically. I can modify the size of it by expanding its left, right, top and bottom until it covers full screen but when I try to do that by simply clicking the maximize button (top right corner, next to the cross) the Window does not occupy the complete screen, the right side stops at an imaginary screen border.
This occurs when the window is maximized; otherwise it appears as normal. Again, the work around would be to re-size the window using sides arrows.
In my mind, this was a Microsoft Windows issue, but I finally find the solution and it seems it has nothing to do with Microsoft.
At least in my case, the problem was with an application Pidgin. The docked Buddy List, even when not showing up, was taking that screen space and blocking the Window from that area. You just need to play with Pidgin a little, (remove the mark on Show buddy list a couple of times did the job for me) Of course if you remove Pidgin it also works but in my case this was not an option.
Special thanks to the user Tinjaw that replied on
