I would like to add however, that I just installed Opera Next, and it fixed the problem. Thanks @Christoph142

The whole point of having the taskbar set to Auto-hide, and having all my windows, (including Opera,) set to maximum, is so that I can see my whole screen when I browse the web, and use various programs without having to press any buttons. I am currently using Juarez's solution to temporarily "fix" the problem, but it is just the same as showing my Taskbar all the time; because of the tabs at the top dropping down below the frame. Opera does a very good job of showing everything when maximized, without having to push any buttons, such as F11, for fullscreen, or the Start key, to show Taskbar. It has only been since Opera23 that this started happening; because, it happened exactly the same on my Desktop, as it did on my laptop, after update from Opera22. PLEASE, update with a workaround. Thank you OpDevs!