--- Operating System, Graphics card ---
Windows 7; AMD 760G, 1600 MB Graphics card memory

--- Blender version with error, and version that worked ---
Blender 2.69, worked with 2.61

--- Short description of error ---
mesh, mirror modifier activated, single or multiple axis, clipping activated, in edit mode: I took a standard cube (tried it with other meshes as well) and moved it away from its pivot point in edit mode. If I now move a vertex to the point where it meets its mirror image using grab, release the vertex and try to move it away again thereafter, it remains fixed to its mirror image. It does not matter, whether merge is activated, or not.

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
The simple blender start screen cube will do. After having moved it away from its pivot point and using the mirror modifier on it, one or more mirroraxises activated, clipping activated as well, click on one or more of the cubes vertices. Then move them to where they meet their mirror images. You may even move them a bit further - it won't make a difference - just to make sure the clipping kicks in. Release vetices. Now try to move them away from their mirror image again. It won't work. They will stay fixed, as if glued to their mirror image. Even with the option merge deactivated. The same thing happens if you don't move them - as previously - using grab, but rather scale the model in edit mode, so the problem seems to be the clipping.