When I upgraded from my Samsung S3 to my new S5, ADB stopped working. After searching a bit, I found this page that explains how to turn on ADB debugging with the new S5 (and KitKat):
http://www.android.gs/how-to-enable-samsung-galaxy-s5-developer-options-and-usb-debugging/
FYI
Hope this saves you some trouble!
Yeah, the 'ole tap on the build number 7 times trick. I thought that was rather funny.
Yeah, anybody who has the attention span to be able to tap on an item 7 times in a row *must* be a developer 
Yeah, the 'ole tap on the build number 7 times trick. I thought that was rather funny.
Yeah, anybody who has the attention span to be able to tap on an item 7 times in a row *must* be a developer