Elvis, I've done this tutorial before but when I drop my final clip into my VT3 Timeline, the black square that covers the logo shows up "grey" in color. I don't remember running into this problem before.
It looks great in PI (invisible) but I was wondering if I need to check something else to make it Superblack.
When you turn on motion blur, some single particles that aren't moving much become semi-transparent, which may be what's happening in your scene. You can duplicate the box's particle type a couple of times to make sure it remains solid.
OK, I tried the same thing without motion blur turned on and got the same results. So, to make sure I'm understanding things correctly, if I duplicate the particle type, this will make the square disappear?
Thanks Elvis, either way, I know I can do this in the end as I've done it before. I just can't figure what I may have done differently.