Having the same problem with the last build. I can even save it in this state! Catch it)))

No, zooming changes nothing. And if my memories does not fail me, the same bug was when I worked on linux. And on another PC.
As I can understand, the bg drawing goes first, and rotating next. So when I stop rotating animation by pressing some key, bg is already on it's place.

I have 32 gb RAM :) I hope, I am not swapping)
And yes, i have McAfee, but can not disable it - do not have an admin privileges.

Here it is

Here it is

Here is blend file. Just apply the bevel, set Segments to 2 (if not set) and switch to UVmap1

Some details, I just noticed.
It happens only when I mix different UV channels

I forgot to say, that after appending object into the new file, problem dasappears.

I'm sorry. Here is the file attached.

Here we have a base cube:
http://s30.postimg.org/kfixd66wh/screenshot_2014_12_08_at_17_05_27.png
We move it to some random location (drag by mouse):
http://s30.postimg.org/nnneq7t69/screenshot_2014_12_08_at_17_07_01.png
Now we duplicate the cube (Shift+D) and then snap it to original. Any vertex to any vertex. Now some of their vertices share one coordinates.
http://s30.postimg.org/83g0zoj1t/screenshot_2014_12_08_at_17_08_41.png
Now they (vertices) are in the same point of space. They should be there even when we will...
...scale both boxes in 100 times (s - 100 - enter):
http://c2n.me/jqZ9tb.png
(sorry, had to change image hosting here :) )
Let's watch on the "shared" vertices from top:
http://c2n.me/jqZe9p.png
Lets zoooooom:
http://c2n.me/jqZfgz.png
This is the main thing what I am talking about. It can even be worse - the vertices of the same cube can be in different coordinates on any axis.

That information is a new thing to me.
I'm sorry for this "bug" then.

There is no need in test file. New subdivided plane can do the thing) Subdivide, select a face, fill with color [in vertex paint mode, of course])

Yes, it happens not every time. In the default cube exuded vertices can even get only half way to the selected snap point) Not the double way, like my example does.

>>So, no active target is available and then, snapping acts like median.
Yes, it has to be.
Here are screenshots, this one shows what i am extruding
http://pix.academ.org/img/2014/07/10/279072db20c0a3fee04c958b4d2f82f7.png
and this one shows where everything flies away and the snapping point
http://pix.academ.org/img/2014/07/10/2ce96b65cc7846dda71d2c0de4331dfd.png
and this is how it used to be
http://pix.academ.org/img/2014/07/10/59db228d798f4f830ffb1ff10f598bde.png

No logic here :(
I use it so often (every day since I learned snapping one million years ago) and now you say, that it is not a bug, but a feature... Just today it threw me away from the work process nearly 10 times...
Some of the newly extruded vertices has to be active. What sense in keeping old vertices active in this situation?
But you are the bosses, of course :(

It has to be fixed, it is impossible to extrude in architecture now :(
And there were no active elements in the older versions. And everything worked great. Logically.
Please, fix it.

I can not reproduce it, i do not even know when this bug happened...