Reply to Recording problem

Hello people ;

Last Saturday I was playing with my s4 and record also , after 1,5 hour I got a problem.deck b was playing and I try to get a song into deck a . It was not possible . Also I try it with other songs .. Nothing
When the song in deck b was ready I try to load a track there . But nothing
What's happen ?

Sorry for my bad English

I play with MacBook pro 2.8 , 8 gig on lion the laptop is from begin 2010
Traktor pro 2 2.1.1