Try right clicking next to your node tree, click apply alpha. Then draw the node to the lower box that just appeared.
NOTE: The comments above are strictly mine, and may not necessarily
represent those of my employers.
Darin Wooldridge
Colorist / Technical Strategist
818-653-3918-cell
dwooldridge@mac.com
check me out at
http://www.facebook.com/pages/Davinci-Resolve-Colorist/117363011609028?ref=....