The layer has no color! (I will make it so it's impossible to leave color empty).
Click on the circle to the right, and type #000 &" enter", for black. (or #fff for white).
That should fix it :)
Ha ha, I didn't even realise the colour was blank! That's fixed it.
Thanks for the speedy replies and the quick fix :)
Anytime :) Let me know if you have any fun ideas that would make Dotgrid better, and I will implement!