if you‘re having this same issue the problem is probably an out-of-date SDK. As of Android 4.2.2 there is a security feature that requires you to confirm the RSA fingerprint of the connecting device. As the following screenshot:
Update ADB TOOL
1. Open the SDK manager and update the tools! Then reboot.
2. OR donwload the ADB from the link:
http://dl.vmall.com/c0b481awh1
http://pan.baidu.com/wap/album/file?uk=2265432600&album_id=153586529128231077&fsid=689995590
Confirm ADB VERSION
Use adb version to check your adb version, and you should work with adb version 1.0.31 and above.
If the version hint is still the old version after adb version command, you‘d better check the adb.exe whether it‘s the old one under the path C:\Windows\System32
Android ADB device offline Issue on Windows
原文：http://my.oschina.net/jerikc/blog/345222