May be your virtual dj software is the crack version or you got software from your friend with serial number. Especially on virtual dj v 6.
To overcome this matter there 2 way of:
First: please go to virtualdj.com then buy your licence if haven't. If your software is legal just contact vdj support.
Second:Re-install your windows xp/vista, Fresh Install with format again. Don't Repair windows because the problem still be same. I have do it. after you finish the install windows xp,sound driver, vga, and more please Install again your virtual dj software but while install: DON'T CONNECT INTERNET, set your internet connection OFFLINE MODE. I don't know may be vdj vendor have give the Bug form network. Very tired for install windows but that is the way it.
So, after you finish istall vdj please go to menu SETUP/CONFIG, then choose tab OPTION--set AUTO UPDATE : DISABLE. After that you free to connect you internet again. I have do it and my friend problem is clear. good luck.