Can't store proxy settings

I have a MBPr and I was trying to configure a proxy on my network settings.
So I opened Network > WiFi > Advanced > Proxies. Checked Web Proxy (HTTP), typed the IP and Port. But when I hit OK, all the settings are lost. If I open the Advanced menu again, the proxy settings are all blank again.
Any idea of what may cause this?

 

First of all, I tried that, but it didn't work either.

Second, I agree that it should only start using the proxy after I apply the new settings, but even after hitting OK, the settings should be saved (but not applied), until I finally decide to apply or discard the changes. Still, the settings are not stored.

 

Yes, it is an Admin account (and the only account), and I just tried repairing the permissions. Still can't save settings :/