rear lift gate will not open

I see you already answered your question, but I've noticed rust at the top of the liftgate strut on my 2007. I cleaned the thick, rubber protectant pad o-ring by sliding it down and cleaned debris behind it. I scraped it off with triple steel wool, wiped the muck clean, and put a layer of white lithium grease and it opens and closes without jerky jamming issue anymore.