Are you using emulate middle mouse button? If yes then you double click to do loop selection.
For me is better to just get a 3 button mouse, instead of fiddling and changing things around. It's like that nightmare, you're somewhere in a big Blender event, they ask you to sit down in front of the whole crowd and show them your awesome Blender skills, and then you're fumbling and confused because you're not used to the default layout and you start sweating and freaking out and you realize you have no way to load up your own configuration and everyone is laughing. Yikes no, you don't want that.
