I have a system that acts funny at least once a week. Every running program randomly spawns extra phantom windows that appear in the taskbar. They don't seem to be actual windows that open on the screen, they're just in the taskbar. They often don't even have titles. When this happens, the system becomes unusable and has to be rebooted. According to AVG and Ad-Aware, it is a clean system. This system was new about four months ago. What could be causing this?