I'm new to Blender, when I was working on a simple character like in the tutorial I'm following. I tried to change the shape of 2 cubes by moving the x and y arrows on the widget but it's not working and it doesn't even give me an arrow shape when I use box select. Does anyone know why this is happening and how I can fix it?
There are three main transformations available: Translate, Rotate, and Scale.
Grab (G) (aka translate/move)
Rotate (R)
Scale (S)
From the wiki:
the normal Transform commands (G for Grab, R for Rotation, S for Scale), can be used to manipulate objects along any axis.
You can also use the the transform manipulator widgets to do this by pressing on the arrows with LMB.
You can enable or disable the transform manipulator widget by pressing the 
icon in 3D view > Header:
Or by pressing CtrlSpace.
You can change the transofm manipulator type by selecting one of the buttons again in the Header of the 3D view:
Location (
)
Rotation (
)
Scale (
)
It sounds like you want Location manipulators, but you have Scale type selected.
Try setting it like this by pressing one of the icons:
Also note that you can select multiple widgets at once by holding Shift while selecting them.
I did change Nvidia to Radeon. After that clicking on the vidget axis doesn't work (it only changes the 3d cursor location). Found this solution on a forum: File-User prefs-System-Selection-OpenGL Select (Not Auto).
It also happened to me. And it wasn't just the gizmo, also de camera orbit wasn't working properly... Finally I discovered that somehow I locked the view to an Object
Deleting the object link made averything work fine again.
