Parts of my GUIs missing

[DarkIceX]

Hey, I've had problems for a long while with parts of the GUI missing. At first, I never paid much attention to it, but now there are even more parts missing, which results in me being unable to close/close/do certain actions on some GUI windows because the background and/or buttons are not visible.

Here's an example of what's happening:


As you can see, parts of the GUI are there, however in this example the background and the buttons are all missing, so that I cannot move or close the GUI. This happens on the servers as well and not just Login.

Can anyone help me out with this? It starts to get annoying when you have a GUI stuck over your screen until you reconnect.