So far I see this looks to me like double click action. Could be a mouse setting or a browser extension. Have you tested another browser?
I cant replicate this behavior but will get few more people involved here.
Firefox, last version: Screenshot by Lightshot
everything is fine, including backend admin.
Last stable version of Opera 21.0 (21.0.1432.67), everything is OK including admin backend.
Safari (5.1.7 for Windows) - cannot test MacOS versions bigger than 6 - 7, but I am pretty sure that Windows version is working fine.
IE...I really don't care or like.
As you said, should be a browser extension, I will discover it as soon is possible and announce you.
I am so sorry for inconvenient, but I really love you guys and your work (I am Romanian