Cannot resize windows The 2 windows/panels I can resize are the ones you get by pressing "T" and "N" 

I'm a blender beginner. I can't seem to resize any window after I create it, neither the properties panel on the right. The double-edged arrow does appear, but when I grab it and move nothing happens.
I'm on Mac.
Please help. 

Edit:
here is a video demonstration of the problem:
https://www.youtube.com/watch?v=rig5zg9l4QQ&amp;feature=youtu.be
Have a look in  File > User Preferences > Input > Screen Editing > and check how you have the  Move Area Edges  setup. 

You need to have this option checked to be able to resize the windows by dragging on the windows edges. Also check to see what the selection method is. Mouse, Left Mouse button.