Reply to Trouble Beat-Gridding?

Working on a Halloween Mashup and decided to use the song "Ghosts n Stuff" by Deadmau5...(Lame and unoriginal, I know)

And for some reason I'm having some serious trouble beatgridding the track. I'll get it on perfectly during the intro and then right when the first drop hits, it goes right off. Anyone have any ideas why? I bought the track on beatport if it helps..

Thanks a bunch