Grab only works in sections (edit mode)

Hello, I have a pretty irritating issue with blender 2.76. Whenever I use the grab-tool inside the edit mode, the object’s movements are limited to the sections on the grid, so it basically jumps from one gab to the other, instead of moving freely.

Any advices?

Turn off snapping (magnet icon on the right hand side of the 3d view header)