I had this problem on my wife's car, turns out a combination of lubricants I've tried in the past actually gummed up the release mechanism. I fixed it by spraying some engine degreaser in there to clean it out real good. That allowed the hood to release and open. Then I rinsed the rest of the de-greaser out of there with a garden hose. Next, use a good lubricant, and spray it on the latch mechanism so its all nice and slick. Worked for me.
