Dragging vertices results in huge jumps and large changes

For some reason, all of a sudden when I try to drag a vertex, rather than moving smoothly with my mouse like it usually, does, nothing happens until I’ve moved the mouse further than usual, and then the vertex jumps a larger distance than I want. I can longer make small changes to my object.

Any idea why?

Sound like you have enabled snapping. Deselect the magnet icon on the 3d view header

That was it, thanks again!