my ddj rb is giving me trouble with rekordbox please help me i just installed new windows and installed the software everything was perfectly installed 
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Are you using a laptop and have you tried using a different USB cable or USB port on your computer? Some PCs don't provide adequate power to the USB port to continue operation of the DDJ-RB, thus it disconnects.
I have the same situation, What is the awnser for this?
Update your Windows to service pack one Windows 7 users..!!
Updates / USB power. Those are the two biggest problems causing disconnects. Please see above.