Weird white box.

Can someone help me here? A weird, draggable white box has appeared on top of my taskbar and it won't go away.
Oddly enough, when I drag shortcuts to it it downloads them. It seems to be a program which hasn't loaded yet, because when I tried Print Screen of Current Program (Alt+PrtScrn), it pastes the white box.
Any suggestions?

Spoiler

Try to restart your computer, or open Task Manager to kill any unknown task.

randomly killing tasks in task manager is NOT a good idea.

Replying to #3

I don't mean processes. Tasks, as in those you can also see in the taskbar.

Restarting worked.

Loonylion · #3randomly killing tasks in task manager is NOT a good idea.

Yeah, you might accidentally (and unknowingly) destroy your computer.