Occasionally - usually very rarely but has happened twice in the last two days - I will have problems where text and icons disappear from the Windows taskbar. For example, if I am using Firefox, the label will vanish from the taskbar, as will the word "start" from the start menu button, the time and most (or all) icons next to it. On the desktop itself, the text for icons loses the shadow that makes them easy to read over the background image. Anything affected usually reappear if I move the mouse over it or select it, but typically vanishes again moments later.
The problem seems to escalate over time - if the computer is left to carry on, desktop icons may vanish entirely or be replaced by a generic (sometimes discoloured) program icon, and an image of the start menu appears at the top of the screen. Folders such as My Documents or My Pictures become unusable, and images opened in Picture and Fax Viewer are replaced with a "Drawing failed" message.
I've never known the problem go away by itself and, fortunately, it has always been fixed by reseting the computer. What I am wondering, though, is whether this may be a symptom of something more sinister. Might something in my PC be about to die? Computers always have little problems, but is this likely to be one to worry about?
(I have noticed that these problems have only ever appeared during hot weather, and since I have moved the computer to a warmer room. Is it possible that these graphical glitches are caused by something as simple as overheating?)