series4: Can't record 2 analog shows

So confused. On our old TIVO we could do this. One VH1 show is recording and I am watching L&O SVU on USA. I tried to record it and it said it would have to stop recording the VH1 show. Huh? What am I missing here. This should be easily doable, right? I mean, I'm watching it, so I should be able to record it.

Thanks,

Stacy