modal dialog box is open

[-= JB =-]

Concerning Modal Dialogs the dictionary says;

While a modal dialog box is open, other windows cannot be edited or  
brought to the front. Because of this, you should use modal dialog  
boxes only when a stack must obtain feedback from the user before it  
can continue.

I am able to open a stack as a modal dialog but from that modal  
dialog stack I am able to
open another stack and it can also be a modal dialog if I want it to be.

So when it says;
other windows cannot be edited or brought to the front.

What windows are they referring to?

Does it mean I should not be able to open a stack as a modal dialog  
from a modal dialog?
Are there potential problems if I do?

thanks,
-=>JB<=-