I have this symptom when I have WP Symposium enabled. It appears the 2 conflict. I have tried every possible configuration with WP Symposium but there seems no easy way currently that the two can work together.
Just seems to have happened after I updated to wordpress 3.3.
I just disabled all my plugins besides for this one…and then i tried again…on posts and pages, still doesnt work.
Well it does work if you copy the htlm code and put it in there…so the actual plugin works 100% just not the short cut link, when you editing a page or post -> you cant click on it, and open it up…and just copy the youtube video link in there. But it’s ok…for now…I just copied the code.
Not to sure what else to do…will try a few more things…also tried to disable and re-enable that plugin as well.