Whenever I middle-mouse click on Steam's main interface it gets unresponsive and baiscally stops working, considering I have some content on my clipboard. Luckly I have a KDE applet shortcut to minimize all windows and show the desktop, but if I hadn't I'd have to close Steam via Ctrl+Alt+F1.

Ways to reproduce:

• Copy some text with Ctrl+C (it gets to the clipboard);
• Middle-mouse click on Steam's interface, probably on some store or community page;

Arch Linux
NVIDIA 340.24
Steam is NOT in any beta participation

System details: http://pastebin.com/wsPzfDNu

I can record a video showing the problem, if the devs are interested.