Samsung Android device won't go in debug mode

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http://stackoverflow.com – I have a simple problem, but thus far all of the advice found on this site and others have not helped. I am trying to debug, through eclipse, on to a samsung device (SCH-R720.) I have done this before with no problem. I recently got a replacement device (same make and model, same sd card) and I have yet to successfully get the phone to enter Debug mode. When it is plugged in, I can see that the USB is connected in my phone's status tray, with the option to copy files to/from my computer (which works fine, by the way) - however, the "Debug mode" message never shows up, and my phone is not s (HowTos)