Reply to Problem with my vci 100

Hi to everyone!!
i need some help about my vestax vci 100.
I want to use my vci 100 with my netbook (Atom N550).But some problem occurred.The first time i istalled Traktor dj studio 3.4 and asio4all drivers and set it with my vci, it worked well.Then i decide to change music,i wanted to play house music and it was impossible to perform. Infact it was difficult to find the exact bpm and the track songs started to work bad.
What could be the cause? And does anyone can suggest a solution on what kind of software i can use?
Thanks!