Cross DJ freeze when routing audio through soundcard

Hey,
I am trying to record a mix through Cross DJ 3.3.11 but every time I try and route the audio through the external sound card (Numark DJ i/o) it effectively crashes the programme.
I have mapped the software to my Mixtrack Pro and everything works fine if the audio is just through my laptop but the moment I select the external device the programme becomes redundant as in tracks won't play- all I can do it joggle the crossfader and watch it move in the programme.
I've had a play around but no joy, any ideas what's going wrong?
Regards,
Finn
I am trying to record a mix through Cross DJ 3.3.11 but every time I try and route the audio through the external sound card (Numark DJ i/o) it effectively crashes the programme.
I have mapped the software to my Mixtrack Pro and everything works fine if the audio is just through my laptop but the moment I select the external device the programme becomes redundant as in tracks won't play- all I can do it joggle the crossfader and watch it move in the programme.
I've had a play around but no joy, any ideas what's going wrong?
Regards,
Finn