It seems that the VML renderer is not updating its bounds (and thus, not updating the geometries' clipping box) when the map is panned around.

To reproduce:

• Open up IE8
• Go to http://leafletjs.com/examples/choropleth.html
• Zoom in a couple of times somewhere
• Pan somewhere
• See how the vector layers are cropped by the bounds of the map previous to the panning

The solution might be to modify the _update method of L.SVG.VML and call this.fire('update') (as done in c931d33 ) so that the vector geometries re-clip themselves.

Anyone wanting to pick this up: fork the repo, clone it locally, apply the suggested fix, run some of the examples in the debug/vector directory with IE8. If successful, submit a pull request.