On Windows, you can see your local user profile folder's .android folder and see if there's a file called 'adbkey'.
Or use 'adb version' to see if you have the latest version. ADB version 1.0.31 is working.
Google just added this in the ADB protocol last November, so you need the NEWEST ADB:
The keys for your hosts are stored at /data/misc/adb/adb_keys, I believe.
If your ADB works correctly, you will see this when you plug in for the first time. You may still have to reseat your cable.
(Pic credit to rickbosch)
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This will not affect all of you.
But on the stock Android 4.2.2 kernel from Google, I cannot get adb to work (always shows 'adb offline') on the stock kernel. This is with my laptop (a Lenovo Thinkpad), and I never had issues with this before with the same setup.
My current workaround is to use a custom kernel for 4.2.2 (thanks to renaud for delivering)
A custom Fugumod kernel that works with 4.2.2 and does not have this issue with ADB:
Stable builds (future?):
Please report back with the PC/Mac and possibly the cable you are using, thanks.