Windows 7, GeForce GT 210
Broken: Blender 2.69.11 #4789793
Worked: Blender 2.69.10 #cc7cfd6
In the Image Editor, I created a new 2048 sq. image.
Pressing the 1-0 number keys did not switch the paint brushes.
Also, holding S and hovering with the mouse did not sample colors from the image.
I restarted blender. I tried these tools in a new file. The issue still persisted.