Problem with ADB on my Nexus 4 (unauthorized phone)
There are two possibilities:


Update your pre 4.2.x SDK to the latest version that includes RSA auth.
If I'm right to assume you're running Linux (user/.android/). In case of Ubuntu/Debian: The 'android-tools-adb' package provides the adb binary which is preferred to that of the SDK. If it is installed, it must be recent (>4.2), because RSA authentication isn't integrated in earlier versions. You can manually download that of Roaring and install it on 12.xx, i have tested this already and it worked. Or just use that from the SDK. Be sure to kill the old adb server instance after upgrading/fixing the version.