It is quite common for Windows to develop strange graphical bugs from time to time. The most common occurrence of this is with multiple monitors of different sizes / resolutions. Windows tries to use lots of clever resizing and scaling techniques to keep your applications rendered cleanly across your different screens but as different monitors are connected/disconnect over time, it can get itself in a mess.
A common symptom is where a black or white box will appear near the top of a screen when a Window is maximised full screen. The box will often cover the window controls (like close/maximise/minimise) so users are unable to resize the window and struggle to continue working. Sometimes though the problem will appear as frozen icons / boxes drawn on the screen or corruption of text and/or icons.
When this problem occurs we recommend the following solutions:
The process is quite simple. You just need to delete the following registry keys (if they exist):
Once deleted, reboot the computer and see if the problem is resolved.