“I need to copy and paste a :30 commercial from a 30 fps time-line to a 24 fps time-line.”
1st things first, this is a bad idea
the difference in frame rates will mess with your content and to a certain extent your edits
what are you trying to achieve?
the problem you are seeing is that you are pasting to a sequence that doe not match your clips aspect ratio,
and maybe not its frame size
a simple way to do it would be to open one of your clips into the viewer,
make a new timeline,
edit the clip into it,
when it asks if you want the new sequence to match , say YES,
the delete the clip,
open the sequence’s settings, and change the frame rate to what you want.
NOW
you can copy from the one sequence into the other.
but as i said the mis-match of frame rates will not be a good thing.
nick