I have a Macbook Pro (Retina) with an external 4K display. I'm running it with the lid closed, i.e., the external display is the only display. OS X 10.9.5.
Normally, it works fine. The past couple days, when I try to resize a window, the window jumps to a different part of the screen, sometimes.
For example, Mail's main window puts itself in the top-right corner. I can move it back to the left side of the screen, but when I try to resize it, as soon as I start to drag the corner, the entire window jumps back to the top right corner of the screen.
Simply moving windows, though, still works correctly.
Short of rebooting (ugh), is there any way to reset OS X's internal concept of how windows should resize?
UPDATE: I unplugged the external display, and it's still happening with the built-in display.