WP 3.5 Update Issue with retina display 2x icons replacing regular ones

I am now on WP 3.5.1 update, but I’m not sure if the issue didn’t first appear at the 3.5 update?.. maybe someone else may confirm.

The issue is that certain images/icons/sprites used by WP in different areas, like:

• the login page WordPress Logo
• the dropdown lists triangle arrow (on the buttons)
• the TinyMCE plugin top dashboard icons/sprite buttons, etc…

…are all looking weird.

I investigated and using Firebug I inspected the elements showing badly. I determined that usually, the associated css for the background-image pulls, for instance:

• background-image: url(“../images/arrows-2x.png?ver=20120916”);

..which is the retina 2x version of the normal image it was using before the WP update.

Manually changing the css in Firebug, like:

• background-image: url(“../images/arrows.png?ver=20120916”);

…fixes the issue.

Somehow, the update wants to serve me retina-display icons, although I am using my regular monitor as always.

This happens on multiple sites (where I updated WP), using multiple browsers (Firefox, Opera, Chrome, IE), but not on the sites that I did not update WP yet.

Also, the sites are hosted on various servers of different providers and the sites use various combinations of different themes/plugins, so I do not think it is any kind of plugins or themes compatibility.

It pretty much looks like WP ‘thinks’ I am using a retina-display, when I am in fact, NOT!

Any kind of advice would be greatly appreciated. Preferably something that doesn’t mean writing code in WP core files.

Thanks in advance!

I don’t know what to do next.